Projector and control method for projector

ABSTRACT

A projector including an electro-optical panel in which a plurality of pixels are arrayed, an optical path shifting element configured to change an optical path of light emitted from the plurality of pixels, and a control circuit configured to control a state of the optical path shifting element such that light emitted from a predetermined pixel among the plurality of pixels reaches a first position on a display screen in the first unit period, control a state of the optical path shifting element such that light emitted from the predetermined pixel reaches a second position on the display screen in the second unit period, and control a state of the optical path shifting element in a transition period in which a unit period transitions from the first unit period to the second unit period based on a type of image indicated by an input image signal

The present application is based on, and claims priority from JPApplication Serial Number 2021-105466, filed. Jun. 25, 2021, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a projector and a control method forthe projector.

2. Related Art

In the technical field of projectors, a pixel shift technology using anoptical path shifting element that optically shifts a display positionis known as a method of artfully increasing a resolution. In the pixelshift technology, one frame period corresponding to a single frame isdivided into a plurality of unit periods, and the optical path shiftingelement is controlled such that the optical path shifting element is ina state differing in each of the unit periods. As a result, the displayposition of an image projected from the projector on the projectionsurface shifts in each unit period.

As a pixel shift technology, for example, JP-A-2011-203460 discloses atechnique of controlling whether to move a position of an image ofpixels on a projection surface over time depending on whether the imageto be displayed is a still image or a moving image. In addition,JP-A-2019-195130 discloses a technique of controlling whether to move aprojection position depending on whether a size of a pixel of aprojected image has a value equal to or greater than a predeterminedvalue.

In the pixel shift technology, it is desirable to instantaneouslyperform a state change of an optical path shifting element and switchingof a projection image in each unit period. However, in reality, acertain amount of time is required for a state change of an optical pathshifting element and switching of a projection image. Therefore, thereis a time lag between the start and end timings of a state change of anoptical path shifting element and the start and end timings of switchingof a projection image. In this case, the image quality of the projectionimage deteriorates. Further, a time required for switching a projectionimage depends on, for example, a response speed of the liquid crystalpanel of a projector.

However, images projected from a projector includes images with agrayscale value changing smoothly among pixels and images with clearboundaries between pixels. Thus, a projector that appropriately performsan image shift regardless of which of the two types of images isprojected is required.

SUMMARY

A projector according to an aspect of the present disclosure includes anelectro-optical panel in which a plurality of pixels that emit lightbased on an image signal are arrayed, an optical path shifting elementthat can change an optical path of light emitted from, the plurality ofpixels, an image processing circuit that supplies a first image signalbased on an input image signal as the image signal to theelectro-optical panel in a first unit period among a plurality of unitperiods included in one frame period and supplies a second image signalbased on the input image signal as the image signal to theelectro-optical panel in a second unit period after the first unitperiod among the plurality of unit periods, and a control circuit thatcontrols a state of the optical path shifting element such that lightemitted from a predetermined pixel among the plurality of pixels reachesa first position on a display screen in the first unit period, controlsa state of the optical path shifting element such that light emittedfrom the predetermined pixel reaches a second position on the displayscreen in the second unit period, and controls, based on a type of imageindicated by the input image signal, a state of the optical pathshifting element in a transition period in which a unit periodtransitions from the first unit period to the second unit period.

In addition, a control method for a projector according to an aspect ofthe present disclosure is a control method for a projector including anelectro-optical panel in which a plurality of pixels that emit lightbased on an image signal are arrayed and an optical path shiftingelement that can change an optical path of light emitted from theplurality of pixels, the control method including supplying a firstimage signal based on an input image signal to the electro-optical panelas the image signal in a first unit period among a plurality of unitperiods included in one frame period and supplying a second image signalbased on the input image signal as the image signal to theelectro-optical panel in a second unit period after the first unitperiod among the plurality of unit periods, and controlling a state ofthe optical path shifting element such that light emitted from apredetermined pixel among the plurality of pixels reaches a firstposition on a display screen in the first unit period, controlling astate of the optical path shifting element such that light emitted fromthe predetermined pixel reaches a second position on the display screenin the second unit period, and controlling, based on a type of imageindicated by the input image signal, a state of the optical pathshifting element in a transition period in which a unit periodtransitions from the first unit period co the second unit period.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a descriptive diagram illustrating an example of aconfiguration of an optical system of a projector according to a firstembodiment.

FIG. 2 is a diagram for describing an operation of an optical pathshifting element according to the first embodiment.

FIG. 3 is a diagram illustrating a relationship between a frame andsubframes according to the first embodiment.

FIG. 4 is a diagram illustrating a relationship between display pixelsand panel pixels according to the first embodiment.

FIG. 5 is a diagram illustrating a relationship between display pixels,projection positions and the like in G according to the firstembodiment.

FIG. 6 is a block diagram illustrating an example of a configuration ofa control system of a projector according to the first embodiment.

FIG. 7 is a descriptive diagram of a relationship between projectionpositions of an optical path shifting element and control signals overtime according to a comparative example.

FIG. 8 is a block diagram illustrating an example of a configuration ofan image processing circuit according to the first embodiment.

FIG. 9A is a descriptive diagram of a relationship between projectionpositions of the optical path shifting element and control signals overtime according to the first embodiment.

FIG. 9B is a descriptive diagram of a relationship between projectionpositions of the optical path shifting element and control signals overtime according to the first embodiment.

FIG. 10 is a descriptive diagram of projection positions of an opticalpath shifting element according to a second embodiment.

FIG. 11 is a descriptive diagram of a relationship between projectionpositions of the optical path shifting element and control signals overtime according to the second embodiment.

FIG. 12 is a descriptive diagram of projection positions of an opticalpath shifting element according to a third embodiment.

FIG. 13A is a descriptive diagram of a relationship between projectionpositions of the optical path shifting element and control signals overtime according to the third embodiment.

FIG. 13B is a descriptive diagram of a relationship between theprojection positions of the optical path shifting element and thecontrol signals over time according to the third embodiment.

FIG. 14 is a descriptive diagram of an example of display of a projectoraccording to the third embodiment.

FIG. 15 is a descriptive diagram of projection positions of an opticalpath shifting element according to a fourth embodiment

FIG. 16 is a descriptive diagram of a relationship between projectionpositions of the optical path shifting element and control signals overtime according to the fourth embodiment.

FIG. 17A is a descriptive diagram of projection positions of an opticalpath shifting element according to a fifth embodiment.

FIG. 17B is a descriptive diagram of projection positions of the opticalpath shifting element according to the fifth embodiment.

FIG. 18 is a descriptive diagram of projection positions of an opticalpath shifting element according to a sixth embodiment.

FIG. 19 is a descriptive diagram of projection positions of an opticalpath shifting element according to a seventh embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A projector and a control method for the projector according toembodiments will be described below with reference to the accompanyingdrawings. Further, in each drawing, the size and scale of each unit aredifferent from the actual size and scale thereof as appropriate.Moreover, the embodiments described below are suitable specific examplesof the disclosure, and various technically preferable limitations areapplied, but the scope of the disclosure is not limited to these modesunless the disclosure is specifically described in the followingdescription as being limiting.

First Embodiment

First, an example of a configuration of a projector 1 according to afirst embodiment of the present disclosure will be described. FIG. 1 isa descriptive diagram illustrating an example of a configuration of theprojector 1. The projector 1 employs overdrive processing and performsan optical pixel shift to be described below.

The projector 1 includes an illumination device 20, a separation opticalsystem 40, three liquid crystal panels 10R, 10G, and 10B, and aprojection optical system 60. Further, although details will bedescribed in FIG. 6 below, the projector 1 includes an optical pathshifting element 100 and functional blocks of a control system thatcontrols the liquid crystal panels 10R, 10G, and 10B, and the like inaddition to the elements illustrated in FIG. 1 . Each of the liquidcrystal panels 10R, 10G, and 10B is an example of an “electro-opticalpanel”. Hereinafter, the liquid crystal panels 10R, 10G, and 10B may becollectively referred to as a liquid crystal panel 10.

The illumination device 20 has a white light source such as a halogenlamp, for example.

The separation optical system 40 includes three mirrors 41, 42, 45, anddichroic mirrors 43 and 44 inside. In addition, the separation opticalsystem 40 separates white light that is visible light emitted from theillumination device 20 into light of the three primary colors of red,green, and blue. Hereinafter, red is referred to as “R”, green isreferred to as “G”, and blue is referred to as “B”.

For example, white light emitted from the illumination device 20 isseparated into light components of the three primary colors of light inthe wavelength range of R, light in the wavelength range of G, and lightin the wavelength range of B by the mirrors 41, 42, and 45 and thedichroic mirrors 43 and 44 disposed inside the separation optical system40. Then, the light in the wavelength range of R is guided to the liquidcrystal panel 10R, the light in the wavelength range of G is guided tothe liquid crystal panel 10G, and the light in the wavelength range of Bis guided to the liquid crystal panel 10B.

Specifically, the dichroic mirror 44 transmits light in the wavelengthrange of R of white light and reflects light in the wavelength ranges ofG and B. The dichroic mirror 43 transmits light in the wavelength rangesof B of the light in the wavelength range of G and B reflected by thedichroic mirror 44 and reflects light in the wavelength range of G.

Here, the liquid crystal panels 10R, 10G, and 10B are used as spatialoptical modulation units, respectively. Each of the liquid crystalpanels 10R, 10G, and 10B includes, for example, 800 data lines, 600scanning lines, and pixels arranged in a matrix shape in which 800pixels in the horizontal direction and 600 pixels in the verticaldirection are arrayed. In addition, in each pixel, the polarizationstate of transmitted light, which is emitted light of incident light, iscontrolled according to the grayscale. Further, the numbers of scanninglines, data lines, and pixels of the liquid crystal panels 10R, 10G, and10B described above are an example, and are not limited to the aboveexample.

The liquid crystal panels 10R, 10G, and 10B are provided with pixelelectrodes each having a substantially square shape corresponding to theintersections of the scanning lines and the data lines, and with counterelectrodes facing the pixel electrodes that are the same for each of thepixels. In addition, VA liquid crystals are provided between the pixelelectrodes and the counter electrodes.

When a certain scanning line is selected in such a configuration, thedata line intersecting the scanning line applies a voltage to the pixelelectrode at the intersection of the scanning line and the data line.Even when the selection of the scanning line is canceled, the appliedvoltage is retained by the capacitor between the pixel electrode and thecounter electrode facing the pixel electrode.

The projection optical system 60 includes a dichroic prism 61, aprojection lens system 62, and the optical path shifting element 100.Light modulated by each of the liquid crystal panels 10R, 10G, and 10Bis incident on the dichroic prism 61 from three directions. While thedichroic prism 61 refracts light in the wavelength range of R and lightin the wavelength range of B at 90 degrees, light in the wavelengthrange of G travels straight therethrough. As a result, the images ofeach of the primary colors of R, G, and B are combined.

Light emitted from the dichroic prism 61 passes through the optical pathshifting element 100 and reaches the projection lens system 62. Forexample, the optical path shifting element 100 is disposed between thedichroic prism 61 and the projection lens system 62.

The projection lens system 62 causes the light emitted from the opticalpath shifting element 100, specifically, the combined image to expandand to be projected on a projection surface 80 such as a screen.Further, the dichroic mirrors 43 and 44 cause light beams correspondingto the primary colors of R, G, and B corresponding to each of thedichroic mirrors to be incident on the liquid crystal panels 10R, 10G,and 10B. For this reason, it is not necessary to provide a color filterin the liquid crystal panels 10R, 10G and 10B.

In addition, while an image transmitted by each of the liquid crystalpanels 10R and 10B is reflected by the dichroic prism 61 and projectedon the projection surface 80, an image transmitted by the liquid crystalpanel 10G travels straight through the dichroic prism 61 and isprojected thereon. Thus, the image formed by the liquid crystal panels10R and 10B and the image formed by the liquid crystal panel 10G arelaterally inverted.

FIG. 2 is a diagram for describing an operation of the optical pathshifting element 100. The optical path shifting element 100 is drivenbased on an output signal of an optical path shifting element drivecircuit 12, and causes the optical path of incident light to deviate toshift the position of the pixel displayed on the projection surface 80.This will be referred to as a pixel shift in the following description.When the optical path of light emitted from the dichroic prism 61 isshifted by the optical path shifting element 100, the position of adisplayed pixel is deviated, i.e., is shifted, on the projection surface80.

Specifically, when a one-frame image is displayed due to ahigh-resolution image signal VIDH to be described later, a period inwhich the one frame is displayed is divided into four subframes, and theprojection position is shifted for each subframe. Due to such a shift,one panel pixel is visually recognized as if the four display pixelswere displayed in one frame, i.e. four subframes.

FIG. 3 is a diagram for describing a relationship between a frame andsubframes in the embodiment. As illustrated in this drawing, the foursubframes created by dividing one frame F are denoted by referencesymbols f1, f2, f3, and f4, respectively, in order of time in theembodiment

Next, a relationship between display pixels with grayscale levelsspecified by the high-resolution image signal VIDH, panel pixels of theliquid crystal panel 10, and projection positions by the optical pathshifting element 100 will be described. Further, although the opticalpath shifting element 100 causes a projection direction from thedichroic prism 61 to be shifted as described above, an amount of shiftis converted into a size of a projection pixel (panel pixel) on theprojection surface 80 for convenience.

The left column in FIG. 4 is a diagram illustrating only some extractedpixels of display pixels indicated by the high-resolution image signalVIDH. Additionally, the right column in FIG. 4 is a diagram illustratingan extracted array corresponding to the array of the display pixels inthe left column among panel pixels of the liquid crystal panel 10.

In order to distinguish pixels in the array of the display pixelsindicated by the high-resolution image signal VIDH in FIG. 4 , referencesymbols A1, B1, A2, B2, A3, and B3 are given from the left side in thefirst row for convenience. Also, D1, C1, D2, C2, D3, and C3 are givenfrom the left side in the second row. Also, A4, B4, A5, B5, A6, and B6are given from the left side in the third row, Also, D4, C4, D5, C5, D6,and C6 are given from the left side in the fourth row. Also, A7, B7, A8,B8, A9, and B9 are given from the left side in the fifth row. Also, D7,C7, D8, C8, D9, and C9 are given from the left side in the sixth row.

In the array of the panel pixels in FIG. 4 , reference symbols Pa1 toPa3 are given in the first row, Pb1 to Pb3 are given in the second row,and Pc1 to Pc3 are given in the third row for convenience in order todistinguish the pixels.

FIG. 4 illustrates that a total of four display pixels of 2×2 indicatedin a thick line frame in the array of the display pixels of the videodata is represented in one panel pixel. For example, the four displaypixels A1, B1, C1, and D1 are represented in the one panel pixel Pa1. Inaddition, for example, the four display pixels A2, B2, C2, and D2 arerepresented in the one panel pixel Pa2.

FIG. 5 is a diagram illustrating what projection positions of thedisplay pixel of G of the high-resolution image signal VIDH are to bedisplayed by the panel pixel of the liquid crystal panel 10Gcorresponding to G among the three colors of R, G, and B in theprojector 1. Specifically, FIG. 5 is a diagram illustrating whichdisplay pixel among the display pixels of FIG. 4 is to be displayed bythe panel pixel of FIG. 4 at a projection position in the subframes f1to f4. The first stage in FIG. 5 indicates that, for example, the panelpixel Pa1 displays information corresponding to the display pixel A1 inthe subframe f1 and projects the display pixel at a first projectionposition. The second stage in FIG. 5 indicates that, for example, thepanel pixel Pa1 displays information corresponding to the display pixelB1 in the next subframe f2 and projects the display pixel at a secondprojection position. The third stage in FIG. 5 indicates that, forexample, the panel pixel Pa1 displays information corresponding to thedisplay pixel C1 in the next subframe f3 and projects the display pixelat a third projection position. The fourth stage in FIG. 5 indicatesthat, for example, the panel pixel Pa1 displays informationcorresponding to the display pixel D1 in the next subframe f4 andprojects the display pixel at a fourth projection position. With thisconfiguration, a high-resolution image can be displayed based on thedisplay pixels A1, B1, C1, and D1 using the panel pixel Pa1 in the oneframe F. In the embodiment, the display pixel A1, the display pixel B1,the display pixel C1, and the display pixel D1 correspond to a firstdisplay pixel, a second display pixel, a third display pixel, and afourth display pixel, respectively. Further, the subframe f1, thesubframe f2, the subframe f3, and the subframe f4 correspond to a “firstunit period”, a “second unit period”, a “third unit period”, and a“fourth unit period”, respectively.

In order to describe a projection position by the optical path shiftingelement 100, the first projection position in the first subframe f1 ofthe frame F will be referred to as a “projection position (A)” forconvenience. Further, the state of the optical path shifting element 100when light emitted from the dichroic prism 61 reaches the projectionposition (A) will be referred to as a “state A”.

In the subframe f1, one panel pixel represents the hatched display pixellocated at the upper left corner among the 2×2 display pixels.Specifically, in the subframe f1, the panel pixels Pa1 to Pa3, Pb1 toPb3, and Pc1 to Pc3 represent the display pixels A1, A2, A3, A4, A5, A6,A7, A8, and A9, respectively, in order. Here, for example, that thepanel pixel Pa1 represents the display pixel A1 means that the panelpixel Pa1 of the liquid crystal panel 10G has a transmittancecorresponding to the grayscale level of the G component in the displaypixels A1 indicated by the high-resolution image signal VIDH.

In the next subframe f2, the optical path shifting element 100 isassumed to be at a “projection position (B)” that is the secondprojection position to which the projection position (A) of the subframef1 indicated by dashed lines has shifted to the right of the drawing by0.5 panel pixels. Further, the state of the optical path shiftingelement 100 when light emitted from the dichroic prism 61 reaches theprojection position (B) will be referred to as a “state B”.

In addition, in the subframe f2, one panel pixel represents the hatcheddisplay pixel located at the upper right corner among the 2×2 displaypixels. Specifically, in the subframe f2, the panel pixels Pa1 to Pa3,Pb1 to Pb3, and Pc1 to Pc3 represent the display pixels B1, B2, B3, B4,B5, B6, B7, B8, and B9, respectively, in order.

In the subframe f3, the optical path shifting element 100 is assumed tobe at a “projection position (C)” that is the third projection positionto which the projection position (B) in the subframe f2 indicated by thedashed lines has shifted downward in the drawing by 0.5 panel pixels.Further, the state of the optical path shifting element 100 when lightemitted from the dichroic prism 61 reaches the projection position (C)will be referred to as a “state C”.

In addition, in the subframe f3, one panel pixel represents the hatcheddisplay pixel located at the lower right corner among the 2×2 displaypixels. Specifically, in the subframe f3, the panel pixels Pa1 to Pa3,Pb1 to Pb3, and Pc1 to Pc3 represent the display pixels C1, C2, C3, C4,C5, C6, C7, C8, and C9, respectively, in order.

In addition, in the subframe f4, the optical path shifting element 100is assumed to be at a “projection position (D)” that is the fourthprojection position to which the projection position (C) in the subframef3 indicated by the dashed lines has shifted to the left of the drawingby 0.5 panel pixels. Furthermore, the state of the optical path shiftingelement 100 when light emitted from the dichroic prism 61 reaches theprojection position (D) will be referred to as a “state D”.

In addition, in the subframe f4, one panel pixel represents the hatcheddisplay pixel located at the lower left corner among the 2×2 displaypixels. Specifically, in the subframe f4, the panel pixels Pa1 to Pa3,Pb1 to Pb3, and Pc1 to Pc3 represent the display pixels D1, D2, D3, D4,D5, D6, D7, D8, and D9, respectively, in order.

After the subframe f4, the optical path shifting element 100 returns tothe projection position (A) to which the projection position (D) of thesubframe f4 indicated by dashed lines has shifted upward in the drawingby 0.5 panel pixels.

A configuration of the control system of the projector 1 will bedescribed below. FIG. 6 is a block diagram illustrating a configurationexample of the control system of the projector 1. The projector 1includes the liquid crystal panels 10R, 10G, and 10B, an imageprocessing circuit 11, the optical path shifting element drive circuit12, a timing control circuit 13, and the optical path shifting element100 as illustrated in the drawing.

The image processing circuit 11 includes an image determination circuit11A that determines the type of an image with the high-resolution imagesignal VIDH as an input image signal. In addition, the image processingcircuit 11 includes a conversion circuit 11B that converts thehigh-resolution image signal VIDH into a low-resolution image signalVIDL. Furthermore, the image processing circuit 11 includes an overdriveprocessing circuit 11C that generates output image signals Dr, Dg, andDb for driving the liquid crystal panels 10R, 10G, and 10B by performingoverdrive processing on the low-resolution image signal VIDL.

The optical path shifting element drive circuit 12 drives the opticalpath shifting element 100 based on a control signal CTL1 supplied fromthe timing control circuit 13. The optical path shifting element drivecircuit 12 is an example of a “control circuit”. Further, the “controlcircuit” may include the timing control circuit 13 described below.

The timing control circuit 13 generates a clock signal and the like forsupplying a data signal to each pixel electrode of the liquid crystalpanels 10R, 10G, and 10B, and supplies the generated clock signal andthe like to a data line drive circuit, which is not illustrated, of theliquid crystal panels 10R, 10G, and 10B. In addition, the timing controlcircuit 13 generates a control signal CTL1 for controlling the opticalpath shifting element drive circuit 12 and a control signal CTL2 forcontrolling the overdrive processing circuit 11C based on the inputhigh-resolution image signal VIDH and a determination signal DET inputfrom the image determination circuit 11A. Further, although thedetermination signal DET is a signal indicating the determination resultof the image indicated by the high-resolution image signal VIDH, detailsthereof will be described below. This configuration makes it possible tocontrol the overdrive processing in synchronization with the state A tothe state D of the optical path shifting element 100 described withreference to FIG. 5 . Further, although the timing control circuit 13performs various control operations based on the high-resolution imagesignal VIDH and the determination signal DET in this example, it mayperform various control operations based on the low-resolution imagesignal VIDL and the determination signal DET output from the conversioncircuit 11B. In addition, the timing control circuit 13 performs timedivision on one frame period corresponding to the one frame constitutedby the state A to the state D into subframes f1 to f4 that are unitperiods each corresponding to the states in FIG. 3 . The optical pathshifting element 100 is in the state A in the first unit period f1 asdescribed above. Additionally, the optical path shifting element 100 isin the state B in the second unit period f2. Additionally, the opticalpath shifting element 100 is in the state C in the third unit period f3.Additionally, the optical path shifting element 100 is in the state D inthe fourth unit period f4.

The control signal CTL1 is more particularly a signal for controllingthe projection position of an image of light emitted from the opticalpath shifting element 100. Hereinafter, a projection position of animage of light emitted from the optical path shifting element 100 willbe referred to as a “projection position by the optical path shiftingelement 100”. The control signal CTL1 includes a control signal CTL1_Xfor causing a projection position to shift vertically and a controlsignal CTL1_Y for causing a projection position to shift horizontally onthe projection surface 80 of the projector 1. Specifically, for aprojection position by the optical path shifting element 100, an upwardor downward direction is specified by a voltage of the control signalCTL1_Y, and a left or right direction is specified by a voltage of thecontrol signal CTL1_X.

As will be more specifically described below, if the voltage of thecontrol signal CTL1_X has a lowest value, the optical path shiftingelement 100 is at the projection position (A) or (D), and if the voltagethereof has a highest value, the optical path shifting element 100 is atthe projection position (B) or (C) with reference to FIG. 5 . If thevoltage of the control signal CTL1_X has a value from the lowest valueto the highest value, the optical path shifting element 100 is at aposition between the projection position. (A) or (D) and the projectionposition (B) or (C) according to the voltage.

In addition, if the voltage of the control signal CTL1_Y has a lowestvalue, the optical path shifting element 100 is at the projectionposition (A) or (B), and if the voltage thereof has a highest value, theoptical path shifting element 100 is at the projection position (C) or(D). If the voltage of the control signal CTL1_Y has a value from thelowest value to the highest value, the optical path shifting element 100is at a position between. the projection position (A) or (B) and theprojection. positon (C) or (D) according to the voltage.

FIG. 7 is a diagram illustrating a relationship between the projectionpositions by the optical path shifting element 100 corresponding to FIG.5 and the control signals CTL1_X and CTL1_Y over time that is arelationship over time as a comparative example. Further, FIG. 7 shows ahighest value of CTL1_X and CTL1_Y at 100V and a lowest value thereof at0V as an example. However, an aspect of the embodiment is not limitedthereto.

Specifically, the voltage of the control signal CTL1_X is maintained atthe lowest value in the period from a timing t0 to a timing t1. Inaddition, the voltage of the control signal CTL1_X increases from thelowest value to the highest value in the period from the timing t1 to atiming t2. Furthermore, the voltage of the control signal CTL1_X ismaintained at the highest value in the period from the timing t2 to atiming t5. Furthermore, the voltage of the control signal CTL1_Xdecreases from the highest value to the lowest value in the period fromthe timing t5 to a timing t6. Furthermore, the voltage of the controlsignal CTL1_X is maintained at the lowest value in the period from thetiming t6 to a timing t9. Furthermore, the voltage of the control signalCTL1_X increases from the lowest value to the highest value in theperiod from the timing t9 to a timing t10.

Furthermore, the voltage of the control signal CTL1_Y is maintained atthe lowest value in the period from the timing t0 to the timing t3.Furthermore, the voltage of the control signal CTL1_Y increases from thelowest value to the highest value in the period from the timing t3 tothe timing t4. Furthermore, the voltage of the control signal CTL1_Y ismaintained at the highest value in the period from the timing t4 to thetiming t7. Furthermore, the voltage of the control signal CTL1_Ydecreases from the highest value to the lowest value in the period fromthe timing t7 to the timing t8. Furthermore, the voltage of the controlsignal CTL1_Y is maintained at the lowest value in the period from thetiming t8 to the timing t10.

Thus, the state of the optical path shifting element 100 is maintainedin the state A in the period from the timing t0 to the timing t1. Alsoat the timing t1, the state of the optical path shifting element 100starts to transition from the state A to the state B. In addition, thestate of the optical path shifting element 100 ends the transition tothe state B at the timing t2. Furthermore, the state of the optical pathshifting element 100 is maintained in the state B in the period from thetiming t2 to the timing t3. Also at the timing t3, the state of theoptical path shifting element 100 starts to transition from the state Bto the state C. In addition, the state of the optical path shiftingelement 100 ends the transition to the state C at the timing t4.Furthermore, the state of the optical path shifting element 100 ismaintained in the state C in the period from the timing t4 to the timingt5. Also at the timing t5, the state of the optical path shiftingelement 100 starts to transition from the state C to the state D. Inaddition, the state of the optical path shifting element 100 ends thetransition to the state D at the timing t6. Furthermore, the state ofthe optical path shifting element 100 is maintained in the state D inthe period from the timing t6 to the timing t7. Also at the timing t7,the state of the optical path shifting element 100 starts to transitionfrom the state D to the state A. The state of the optical path shiftingelement 100 ends the transition to the state A at the timing t8.Furthermore, the state of the optical path shifting element 100 ismaintained in the state A in the period from the timing t8 to the timingt9. Also at the timing t9, the state of the optical path shiftingelement 100 starts to transition from the state A to the state B. Thestate of the optical path shifting element 100 ends the transition tothe state B at the timing t10.

Next, a detailed configuration of the image processing circuit 11 willbe described. FIG. 8 is a block diagram illustrating a configurationexample of the image processing circuit 11.

The image determination circuit 11A determines the type of an imageindicated by the high-resolution image signal VIDH based on thehigh-resolution image signal VIDH. Types of images correspond to, forexample, an image with clear boundaries between pixels, and an imagewith unclear boundaries between pixels. An image with clear boundariesbetween pixels is an image that is to be expressed with the pixelsseparated from each other. In addition, an image with unclear boundariesbetween pixels is an image in which grayscale values change smoothlybetween pixels. It is assumed in the embodiment that an image with clearboundaries between pixels is a character drawing and an image withunclear boundaries between pixels is a natural image. However, an imagewith clear boundaries between pixels is not limited to a characterdrawing. Similarly, an image with unclear boundaries between pixels isnot limited to a natural image.

Additionally, the image determination circuit 11A generates adetermination signal DET indicating the determination result, andoutputs the generated determination signal DET to the timing controlcircuit 13.

Although a method for determining the type of an image is notparticularly limited, for example, the image determination circuit 11Amay determine whether the high frequency component contained in oneimage indicated by the high-resolution image signal VIDH exceeds athreshold value, and generate the determination signal DET indicatingthe determination result. Specifically, when the high frequencycomponent contained in one image exceeds the threshold value, thedetermination signal DET indicates that the image is an image withunclear boundaries between the pixels. On the other hand, when the highfrequency component contained in one image does not exceed the thresholdvalue, the determination signal DET indicates that the image is an imagewith clear boundaries between pixels.

Alternatively, the image determination circuit 11A calculates thehorizontal difference value which is the absolute value of thedifference in luminance between pixels adjacent to each other in thehorizontal direction for each image of R, G, and B constituting the oneimage indicated by the high-resolution image signal VIDH as anothermethod. Next, the image determination circuit 11A calculates thevertical difference value which is the absolute value of the differencein luminance between pixels adjacent to each other in the verticaldirection for each image of R, G, and B. Next, the image determinationcircuit 11A calculates the total difference value by adding the sum ofthe horizontal difference values and the sum of the vertical differencevalues. Finally, the image determination circuit 11A may compare thetotal of the total difference values of each image of R, G, and B and athreshold value to generate the determination signal DET. Specifically,if the total of the total difference values of each image of R, G, and Bexceeds the threshold value, the determination signal DET indicates thatthe image is an image with clear boundaries between pixels. On the otherhand, if the total of the total difference values of each image of R, G,and B does not exceed the threshold value, the determination signal DETindicates that the image is an image with unclear boundaries betweenpixels.

Alternatively, as another method, when information indicating the typeof the one image indicated by the high-resolution image signal VIDH isadded to the high-resolution image signal VIDH, the image determinationcircuit 11A may generate the determination signal DET based on the addedinformation.

As described above, the determination signal DET is output to the timingcontrol circuit 13. The timing control circuit 13 generates a controlsignal CTL1 for controlling the optical path shifting element drivecircuit 12 based on the high-resolution image signal VIDH and thedetermination signal DET acquired from the image determination circuit11A.

Before describing the conversion circuit 11B and the like, therelationship between a determination result by the image determinationcircuit 11A and a projection position by the optical path shiftingelement 100 will be described with reference to FIGS. 9A and 9B.

FIGS. 9A and 9B are diagrams illustrating an example of the relationshipbetween a projection position by the optical path shifting element 100and the control signals CTL1_X and CTL1_Y over time for eachdetermination result by the image determination circuit 11A according tothe embodiment. Further, FIGS. 9A and 9B shows a highest value of CTL1_Xand CTL1_Y at 100V, and a lowest value thereof at 0V as an example.However, an aspect of the embodiment is not limited thereto. Inaddition, FIG. 9A illustrates a case where the image determinationcircuit 11A has determined that an image indicated by thehigh-resolution image signal VIDH is an image to be expressed withpixels separated from each other. On the other hand, FIG. 9B illustratesa case where the image determination circuit 11A has determined at theimage an image indicated by the high-resolution image signal VIDH withgrayscale values smoothly changing between pixels. However, anembodiment of the present disclosure is not limited thereto.Additionally, although FIG. 9A illustrates a case of a character drawingas a former example, and FIG. 9B illustrates a case of a natural imageas a latter example, an embodiment of the present disclosure is notlimited thereto. Further, as will be described in embodiments from asecond embodiment, the case of a character drawing will be described asa former example, and the case of a natural image will be described as alatter example.

When the determination result by the image determination circuit 11A isa character drawing, the voltage of the control signal CTL1_X ismaintained at the lowest value in the period from a timing t20 to atiming t21. Furthermore, the voltage of the control signal CTL1_Xincreases from the lowest value to the highest value in the period fromthe timing t21 to a timing t22. Furthermore, the voltage of the controlsignal CTL1_X is maintained at the highest value in the period from thetiming t22 to a timing t25. Furthermore, the voltage of the controlsignal CTL1_X decreases from the highest value to the lowest value inthe period from the timing t25 to a timing t26. Furthermore, the voltageof the control signal CTL1_X is maintained at the lowest value in theperiod from the timing t26 to a timing t29. Furthermore, the voltage ofthe control signal CTL1_X increases from the lowest value to the highestvalue in the period from the timing t29 to a timing t30.

Furthermore, the voltage of the control signal CTL1_Y is maintained atthe lowest value in the period from the timing t20 to a timing t23.Furthermore, the voltage of the control signal CTL1_Y increases from thelowest value to the highest value in the period from the timing t23 to atiming t24. Furthermore, the voltage of the control signal CTL1_Y ismaintained at the highest value in the period from the timing t24 to atiming t27. Furthermore, the voltage of the control signal CTL1_Ydecreases from the highest value to the lowest value in the period fromthe timing t27 to a timing t28. Furthermore, the voltage of the controlsignal CTL1_Y is maintained at the lowest value in the period from thetiming t28 to the timing t30.

Thus, the state of the optical path shifting element 100 is maintainedin the state A in the period from the timing t20 to the timing t21. Alsoat the timing t21, the state of the optical path shifting element 100starts to transition from the state A to the state B. In addition, thestate of the optical path shifting element 100 ends the transition tothe state B at the timing t22. Furthermore, the state of the opticalpath shifting element 100 is maintained in the state B in the periodfrom the timing t22 to the timing t23. Also at the timing t23, the stateof the optical path shifting element 100 starts to transition from thestate B to the state C. In addition, the state of the optical pathshifting element 100 ends the transition to the state C at the timingt24. Furthermore, the state of the optical path shifting element 100 ismaintained in the state C in the period from the timing t24 to thetiming t25. Also at the timing t25, the state of the optical pathshifting element 100 starts to transition from the state C to the stateD. In addition, the state of the optical path shifting element 100 endsthe transition to the state D at the timing t26. Furthermore, the stateof the optical path shifting element 100 is maintained in the state D inthe period from the timing t26 to the timing t27. Also at the timingt27, the state of the optical path shifting element 100 starts totransition from the state D to the state A. The state of the opticalpath shifting element 100 ends the transition to the state A at thetiming t28. Furthermore, the state of the optical path shifting element100 is maintained in the state A in the period from the timing t28 tothe timing t29. Also at the timing t29, the state of the optical pathshifting element 100 starts to transition from the state A to the stateB. The state of the optical path shifting element 100 ends thetransition to the state B at the timing t30.

On the other hand, when the determination result by the imagedetermination circuit 11A is a natural image, the voltage of the controlsignal CTL1_X is maintained at the lowest value in a period from atiming t40 to a timing t41. In addition, the voltage of the controlsignal CTL1_X increases from the lowest value to the highest value inthe period from the timing t41 to a timing t42. Furthermore, the voltageof the control signal CTL1_X is maintained at the highest value in theperiod from the timing t42 to a timing 45. Furthermore, the voltage ofthe control signal CTL1_X decreases from the highest value to the lowestvalue in the period from the timing t45 to a timing t46. Furthermore,the voltage of the control signal CTL1_X is maintained at the lowestvalue in the period from the timing t46 to a timing t49. Furthermore,the voltage of the control signal CTL1_X increases from the lowest valueto the highest value in the period from the timing t49 to a timing t50.

Furthermore, the voltage of the control signal CTL1_Y is maintained atthe lowest value in the period from the timing t40 to a timing t43.Furthermore, the voltage of the control signal CTL1_Y increases from thelowest value to the highest value in the period from the timing t43 to atiming t44. Furthermore, the voltage of the control signal CTL1_Y ismaintained at the highest value in the period from the timing t44 to atiming t47. Furthermore, the voltage of the control signal CTL1_Ydecreases from the highest value to the lowest value in the period fromthe timing t47 to a timing t48. Furthermore, the voltage of the controlsignal CTL1_Y is maintained at the lowest value in the period from thetiming t48 to the timing t50.

Thus, the state of the optical path shifting element 100 is maintainedin the state A in the period from the timing t40 to the timing t41. Alsoat the timing t41, the state of the optical path shifting element 100starts to transition from the state A to the state B. In addition, thestate of the optical path shifting element 100 ends the transition tothe state B at the timing t42. Furthermore, the state of the opticalpath shifting element 100 is maintained in the state B in the periodfrom the timing t42 to the timing t43. Also at the timing t43, the stateof the optical path shifting element 100 starts to transition from thestate B to the state C. In addition, the state of the optical pathshifting element 100 ends the transition to the state C at the timingt44. Furthermore, the state of the optical path shifting element 100 ismaintained in the state C in the period from the timing t44 to thetiming t45. Also at the timing t45, the state of the optical pathshifting element 100 starts to transition from the state C to the stateD. In addition, the state of the optical path shifting element 100 endsthe transition to the state D at the timing t46. Furthermore, the stateof the optical path shifting element 100 is maintained in the state D inthe period from the timing t46 to the timing t47. Also at the timingt47, the state of the optical path shifting element 100 starts totransition from the state D to the state A. The state of the opticalpath shifting element 100 ends the transition to the state A at thetiming t48. Furthermore, the state of the optical path shifting element100 is maintained in the state A in the period from the timing t48 tothe timing t49. Also at the timing t49, the state of the optical pathshifting element 100 starts to transition from the state A to the stateB. The state of the optical path shifting element 100 ends thetransition to the state B at the timing t50.

As described above, the optical path shifting element 100 transitionsfrom the state A to the state D via the state B and the state C,similarly to the comparative example described in FIG. 7 describedabove.

The periods in which pixels shift, that is, the periods in thetransition state, are the period from the timing t21 to the timing t22,the period from the timing t23 to the timing t24, the period from thetiming t25 to the timing t26, the period from the timing t27 to thetiming t28, and the period from the timing t29 to the timing t30 whenthe determination result by the image determination circuit 11A is acharacter drawing. All of these periods are assumed to have an equallength that is a value “a”. On the other hand, when the determinationresult by the image determination circuit 11A is a natural image, theperiods in which pixel shift, that is, the period in the transitionstate, are the period from the timing t41 to the timing t42, the periodfrom the timing t43 to the timing t44, the period from the timing t45 tothe timing t46, the period from the timing t47 to the timing t48, andthe period from the timing t49 to timing t50. All of these periods areassumed to have an equal length that is a value “b”. Here, when thevalues a and b are compared, a is smaller than b. That is, when the typeof the projected image is a natural image, the optical path shiftingelement 100 is controlled such that the state of the optical pathshifting element 100 changes gently compared to when the projected imageis a character drawing. For this reason, when the type of the projectedimage is a natural image, the projection position by the optical pathshifting element 100 is slowly changed compared to when the projectedimage is a character drawing. Due to the slow change in the projectionposition by the optical path shifting element 100, the expression nearthe boundaries included in the projected image changes gently.Conversely, when the type of a projected image is a character drawing,the optical path shifting element 100 is controlled such that the stateof the optical path shifting element 100 changes quickly, compared towhen the projected image is a natural image. For this reason, when thetype of the projected image is a character image, the projectionposition by the optical path shifting element 100 is quickly changedcompared to when the projected image is a natural image. Due to thequick change in the projection position by the optical path shiftingelement 100, the expression near the boundaries included in theprojected image suddenly changes. Due to this configuration, a degree ofseparation between pixels can be switched based on the type of an imagedisplayed by the projector 1 in the embodiment.

Further, although the example in which the optical path shifting elementdrive circuit 12 controls a speed of change when changing a state of theoptical path shifting element 100 has been introduced in FIGS. 9A and9B, the optical path shifting element drive circuit 12 may control anamount of change, or may control both conditions.

The description will now return to FIG. 8 . The conversion circuit 11Bconverts the high-resolution image signal VIDH into a low-resolutionimage signal VIDL. Further, as an example, the high-resolution imagesignal VIDH is an image signal indicating an image having 1600horizontal pixels and 1200 vertical pixels. In addition, as an example,the low-resolution image signal VIDL is an image signal indicating animage having 800 horizontal pixels and 600 vertical pixels. Theconversion circuit 11B includes a frame memory 111 capable of storingthe high-resolution image signal VIDH in one screen, and generates alow-resolution image signal VIDL using the frame memory 111. Thehigh-resolution image signal VIDH and the low-resolution image signalVIDL are each made from signals of R, G, and B.

In the following description, low-resolution image signals VIDL eachcorresponding to the state A, state B, state C, and state D may bereferred to image signals Va, Vb, Vc, and Vd, respectively.

The overdrive processing circuit 11C illustrated in FIG. 8 includes aprocessing unit Ur that processes the low-resolution image signal VIDLof R, a processing unit Ug that processes the low-resolution imagesignal VIDL of G, and a processing unit Ub that processes thelow-resolution image signal VIDL of B. Although the processing unit Urwill be described below, the processing units Ug and Ub are configuredsimilarly to the processing unit Ur.

The processing unit Ur includes a low-resolution frame memory 112, alook-up table LUT, and a selection circuit 113. A storage capacity ofthe low-resolution frame memory 112 is less than a storage capacity ofthe storage region of the frame memory 111 described above for storingthe high-resolution image signal VIDH of R. For example, a storagecapacity of the low-resolution frame memory 112 is a quarter of thestorage capacity of the frame memory 111. Further, the low-resolutionframe memory 112 may include a storage capacitor that stores at least alow-resolution image signal VIDL for one screen.

The look-up table LUT is supplied with a current low-resolution imagesignal VIDL and a low-resolution image signal VIDL for one previous unitperiod read from the low-resolution frame memory 112. In the followingdescription, the current low-resolution image signal VIDL will bereferred to as a first image signal Vx, and the previous low-resolutionimage signal VIDL will be referred to as a second image signal Vy.

The look-up table LUT stores the first image signal Vx and the secondimage signal Vy and an image signal Dod for overdrive in associationwith each other. For example, the image signal Dod is given in thefollowing equation [1].

Dod=f₁ (Vx, Vy)   [1]

The function f₁ is determined to obtain a desired grayscale for theliquid crystal panel 10 considering response characteristics of liquidcrystal This compensates for and improves the response characteristicsof the liquid crystal panel 10. Further, for example, when the responsedelay time of the liquid crystal panel is 10 ms, the response delay timeis not required to be 0 ms, and if it is shorter than 10 ms, theresponse characteristics of the liquid crystal panel are compensatedfor.

If a grayscale indicated by the first image signal Vx is “100” and agrayscale indicated by the second image signal Vy is “10” in overdriveprocessing, a grayscale indicated by the image signal Dod is greaterthan “100”. This is because, even if the voltage corresponding to thegrayscale is applied to the liquid crystal, it takes time to give aresponse, and thus, the delay time of the liquid crystal is expected sothat it is compensated for. For this reason, she image signal Dod is setto have a greater grayscale than “100” that is the original grayscale.On the other hand, if a grayscale indicated by the first image signal Vxis “100” and a grayscale indicated by the second image signal Vy is“100”, a grayscale indicated by the image signal Dod is “100”. Thereason for this is that it is not necessary to compensate for theresponse characteristics because the current grayscale and the previousgrayscale are equal.

In the state B to the state D of the optical path shifting element 100,the image signals Vb, Vc, and Vd are supplied so the look-up table LUTas the first image signal Vx, and the image signals Va, Vb, and Vc aresupplied to the look-up table LUT as the second image signal Vy. Here,in the frame immediately before the corresponding frame, if thelow-resolution image signal VIDL in the state D of she optical pathshifting element 100 is indicated by an image signal Vd′, the secondimage signal Vy is an image signal Vd′ in the state A of the frame.

Overdrive processing is performed based on the low-resolution imagesignal VIDL (Vx) of a target pixel that is subject to the overdriveprocessing and the low-resolution image signal VIDL (Vy) of the targetpixel in the previous state of the optical path shifting element 100. Asdescribed above, because the low-resolution frame memory 112 holds thelow-resolution image signal VIDL for at least one screen, thelow-resolution image signal VIDL of the target pixel in the previousstate of the optical path shifting element 100 is identified for thetarget pixel that is subject to the overdrive processing.

Next, while the selection circuit 113 illustrated in FIG. 8 selects theimage signal Dod when the overdrive processing is valid, the selectioncircuit 113 selects the first image signal Vx when the overdriveprocessing is not valid to generate an output image signal Dr. Theoverdrive processing being valid or invalid and a processing methodthereof are specified by the control signal CTL2.

As described above, the control signal CTL2 is generated by the timingcontrol circuit 13 based on the high-resolution image signal VIDH andthe determination signal DET input from the image determination circuit11A. Specifically, when the determination result indicated by thedetermination signal DET is an image with clear boundaries betweenpixels, the timing control circuit 13 generates a control signal CTL2such that overdrive processing is performed at a higher response speedfrom the liquid crystal after a voltage is applied to the liquid crystalcompared to when the determination result is an image with unclearboundaries between pixels. Because the response speed from the liquidcrystal made after a voltage is applied to the liquid crystal becomeshigher, the projection position by the optical path shifting element 100changes more quickly. Due to the quicker change in the projectionposition by the optical path shifting element 100, the expression nearthe boundaries included in the projected image suddenly changes.

Further, in a case of an image with unclear boundaries between pixels,the control signal CTL2 may be a control signal for performing theoverdrive processing, or may be a control signal for not performing theoverdrive processing. Specifically, the control signal CTL2 may be acontrol signal for performing the overdrive processing such that theoutput image signal Dr is equal to Dod in the case of an image withunclear boundaries between pixels, and the output image signal Dr isgreater than Dod in the case of an image with clear boundaries betweenpixels. Alternatively, the control signal CTL2 may be a control signalfor performing the overdrive processing such that the output imagesignal Dr is smaller than Dod in the case of an image with unclearboundaries between pixels, and the output image signal Dr is equal toDod in the case of an image with clear boundaries between pixels.

In the pixel shift technology for projectors of the related art, it isnot possible to switch a state of the optical path shifting element 100based on whether it is desirable for an image to be displayed torepresent a video with the pixels separated from each other. On theother hand, the projector 1 according to the embodiment includes theoptical path shifting element drive circuit 12 that controls a state ofthe optical path shifting element 100 in a transition period in which,among a plurality of unit periods included in one frame period, theelement transitions from a first unit period f1 to a second unit periodf2 based on the type of the image indicated by the input image signal.In this way, in a case where the projector 1 according to the embodimentdisplays an image to be expressed with the pixel separated from eachother, the projector can display the image with clear boundaries on theprojection surface 80. Additionally, when an image with unclearboundaries between pixels is to be displayed, the projector 1 accordingto the embodiment can display the image on the projection surface 80such that the grayscale values change smoothly between the pixels.Furthermore, the projector 1 according to the embodiment can perform theimage shift appropriately even when any image is to be displayed on theprojection surface 80.

Additionally, the timing control circuit 13 described above controls aspeed of change of the state of the optical path shifting element 100 inthe transition period described above based on the type of image. Theprojector 1 according to the embodiment is capable of controlling aspeed of change of a state of the optical path shifting element 100 inthe transition period in which the element transitions from the firstunit period f1 to the second unit period f2 based on the type of image,and thus can display the image with clear boundaries on the projectionsurface 80 when the image to be expressed with the pixels separated fromeach other is to be displayed. Additionally, when the image with unclearboundaries between pixels is to be displayed, the projector 1 accordingto the embodiment can display the image on the projection surface 80such that the grayscale values change smoothly between the pixels.

Furthermore, the overdrive processing circuit 11C adjusts thecompensation amount determined due to the overdrive processing based onthe type of image. This allows the projector 1 according to theembodiment to change the overdrive processing to change the speed of aresponse of the liquid crystal based on the type of image to bedisplayed. Furthermore, the projector 1 according to the embodiment hasthe pixels separated from each other to display an image with clearboundaries between pixels, but can display the image with unclearboundaries between pixels more smoothly.

In addition, the image determination circuit 11A uses a difference valuein luminance between the adjacent pixels to identify the type of theimage and outputs the type information indicating the identificationresult to the timing control circuit 13. This enables the projector 1according to the embodiment to identify the type of the image based onthe difference value in luminance between the pixels and to change thestate of the optical path shifting element 100 based on the identifiedtype of the image.

Second Embodiment

Next, a drive method for the projector 1 according to the secondembodiment of the present disclosure will be described with reference toFIGS. 10 and 11 . Hereinafter, a difference between the drive method forthe projector 1 according to the second embodiment and the drive methodfor the projector 1 according to the first embodiment will be mainlydescribed.

FIG. 10 is a diagram illustrating states of the optical path shiftingelement 100, specifically, projection positions by the optical pathshifting element 100. To be specific, “A”, “B”, “C”, and “D” on the leftside in FIG. 10 correspond to “A1”, “B1”, “C1”, and “D1” illustrated inFIG. 5 , respectively, as an example. In addition, “A”, “B”, “C”, and“D” on the right side in FIG. 10 correspond to “A2”, “B2”, “C2”, and“D2” illustrated in FIG. 5 , respectively, as an example.

FIG. 11 is a diagram illustrating a relationship between the projectionpositions by the optical path shifting element 100 and the controlsignals CTL1_X and CTL1_Y over time that is a relationship over time indisplay of a natural image. Further, FIG. 11 shows a highest value ofCTL1_X and CTL1_Y at 100V and a lowest value thereof at 0V as anexample. However, an aspect of the embodiment is not limited thereto. Inaddition, because the relationship between the projection positions ofthe optical path shifting element 100 and the control signals CTL1_X andCTL1_Y over time in display of a character drawing is similar to that ofthe first embodiment, description thereof will be omitted. In a thirdembodiment to a seventh embodiment to be described below, description ofthe relationship between the projection positions of the optical pathshifting element 100 and the control signals CTL1_X and CTL1_Y over timein display of the character drawing will be omitted as well.

A transition state a is set between the state A and the state B indisplay of a natural image display by the projector 1 as illustrated inFIG. 10 . More specifically, a transition period T1 corresponding to thetransition state a is set between the first unit period f1 correspondingto the state A and the second unit period f2 corresponding to the stateB. Similarly, a transition state b is set between the state B and thestate C. More specifically, a transition period T2 corresponding to thetransition state b is set between the second unit period f2corresponding to the state B and the third unit period f3 correspondingto the state C. Similarly, a transition state c is set between the stateC and the state D. More specifically, a transition period T3corresponding to the transition state c is set between the third unitperiod f3 corresponding to the state C and the fourth unit period f4corresponding to the state D. Similarly, a transition state d is setbetween the state C and the state D. More specifically, a transitionperiod T4 corresponding to the transition state d is set between thefourth unit period f4 corresponding to the state D and the unit periodf1 corresponding to the state A.

In addition, a projection position (a) while the state of the opticalpath shifting element 100 is the transition state a is the midpointbetween the projection position (A) and the projection position (B).Similarly, a projection position (b) while the state of the optical pathshifting element 100 is the transition state b is the midpoint betweenthe projection position (B) and the projection position (C). Similarly,a projection position (c) while the state of the optical path shiftingelement 100 is the transition state c is the midpoint between theprojection position (C) and the projection position (D). Similarly, aprojection position (d) while the state of the optical path shiftingelement 100 is the transition state d is the midpoint between theprojection position (D) and the projection position (A).

Further, for example, an intermediate image of the image displayed whilethe state of the optical path shifting element 100 is the state A andthe image displayed while the state thereof is the state B may bedisplayed while the state is in the transition state a. Specifically,when the output image signal Dr differs between while the state of theoptical path shifting element 100 is the state A and the state is thestate B, the output image signal Dr while the state of the optical pathshifting element 100 is the transition state a maybe an intermediatesignal of the output image signal Dr while the state is the state A andthe output image signal Dr while the state is the state B. The outputimage signals Dg and Db while the state of the optical path shiftingelement 100 is the transition state a are also determined in a similarmethod to that for the output image signal Dr.

Alternatively, as an example, the image signal Dod for overdriving whilethe state of the optical path shifting element 100 is the transitionstate a may be a signal having a higher output value than theintermediate signal of the output image signal Dr while the state is thestate A and the output image signal Dr while the state is the state B.Alternatively, as an example, the image signal Dod for the overdrivingwhile the state of the optical path shifting element 100 is thetransition state a may be calculated using the above formula [1] withthe low-resolution image signal VIDL in the state B set as the firstimage signal Vx and the low-resolution image signal VIDL in the state Aset as the second image signal Vy.

Although the operation performed while the state of the optical pathshifting element 100 is the transition state a has been described above,the projector 1 performs similar operations while the state of theoptical path shifting element 100 is one of the transition states b tod. That is, when an image to be displayed differs between while thestate of the optical path shifting element 100 is the state B and thestate thereof is the state C, an intermediate image of the imagedisplayed while the state of the optical path shifting element 100 isthe state B and the image displayed while the state is the state C maybe displayed while the optical path shifting element 100 is in thetransition state b. Similarly, when an image to be displayed differsbetween while the state of the optical path shifting element 100 is thestate C and the state thereof is the state D, an intermediate image ofthe image displayed while the state of the optical path shifting element100 is the state D and the image displayed while the state is the stateC may be displayed while the state is in the transition state c.Similarly, when an image to be displayed differs between while the stateof the optical path shifting element 100 is the state D and the statethereof is the state A, an intermediate image of the image displayedwhile the state of the optical path shifting element 100 is the state Dand the image displayed while the state is the state A may be displayedwhile the optical path shifting element 100 is in the transition stated.

When the determination result by the image determination circuit 11A isa natural image, the voltage of the control signal CTL1_X increases fromthe lowest value to an intermediate value in the period from a timingt60 to a timing t61 as illustrated in FIG. 11 . Furthermore, the voltageof the control signal CTL1_X is maintained at the intermediate value inthe period from the timing t61 to a timing t62. Furthermore, the voltageof the control signal CTL1_X increases from the intermediate value tothe highest value in the period from the timing t62 to a timing t63.Furthermore, the voltage of the control signal CTL1_X is maintained atthe highest value in the period from the timing t63 to a timing t68.Furthermore, the voltage of the control signal CTL1_X decreases from thehighest value to the intermediate value in the period from the timingt68 to a timing t69. Furthermore, the voltage of the control signalCTL1_X is maintained at the intermediate value in the period from thetiming t69 to a timing t70. Furthermore, the voltage of the controlsignal CTL1_X decreases from the intermediate value to the lowest valuein the period from the timing t70 to a timing t71. Furthermore, thevoltage of the control signal CTL1_X is maintained at the lowest valuein the period from the timing t71 to a timing t76. Furthermore, thevoltage of the control signal CTL1_X increases front the lowest value tothe intermediate value in the period from the timing t76 to a timingt77.

Furthermore, the voltage of the control signal CTL1_Y is maintained atthe lowest value in the period from the timing t60 to a timing t64.Furthermore, the voltage of the control signal CTL1_Y increases from thelowest value to the intermediate value in the period from the timing t64to a timing t65. Furthermore, the voltage of the control signal CTL1_Yis maintained at the intermediate value in the period from the timingt65 to a timing t66. Furthermore, the voltage of the control signalCTL1_Y increases from the intermediate value to the highest value in theperiod from the timing t66 to a timing t67. Furthermore, the voltage ofthe control signal CTL1_Y is maintained at the highest value in theperiod from the timing t67 to a timing t72. Furthermore, the voltage ofthe control signal CTL1_Y decreases from the highest value to theintermediate value in the period from the timing t72 to a timing t73.Furthermore, the voltage of the control signal CTL1_Y is maintained atthe intermediate value in the period from the timing t73 to a timingt74. Furthermore, the voltage of the control signal CTL1_Y decreasesfrom the intermediate value to the lowest value in the period from thetiming t74 to a timing t75. Furthermore, the voltage of the controlsignal CTL1_Y is maintained at the lowest value in the period from thetiming t75 to the timing t77.

Thus, the state of the optical path shifting element 100 starts totransition from the state A to the transition state a at the timing t60.Furthermore, the state of the optical path shifting element 100 ends thetransition to the transition state a at the timing t61. Furthermore, thestate of the optical path shifting element 100 is maintained in thetransition state a in the period from the timing t61 to the timing t62.Also at the timing t62, the state of the optical path shifting element100 starts to transition from the transition state a to the state B.Furthermore, the state of the optical path shifting element 100 ends thetransition to the state B at the timing t63. Furthermore, the state ofthe optical path shifting element 100 is maintained in the state B inthe period from the timing t63 to the timing t64. Also at the timingt64, the state of the optical path shifting element 100 starts totransition from the state B to the transition state b. Furthermore, thestate of the optical path shifting element 100 ends the transition tothe transition state b at the timing t65. Furthermore, the state of theoptical path shifting element 100 is maintained in the transition stateb in the period from the timing t65 to the timing t66. Also at thetiming t66, the state of the optical path shifting element 100 starts totransition from transition state b to the state C. In addition, thestate of the optical path shifting element 100 ends the transition tothe state C at the timing t67. Furthermore, the state of the opticalpath shifting element 100 is maintained in the state C in the periodfrom the timing t67 to the timing t68. Also at the timing t68, the stateof the optical path shifting element 100 starts to transition from thestate C to the transition state c. Furthermore, the state of the opticalpath shifting element 100 ends the transition to the transition state cat the timing t69. Furthermore, the state of the optical path shiftingelement 100 is maintained in the transition state c in the period fromthe timing t69 to the timing t70. Also at the timing t70, the state ofthe optical path shifting element 100 starts to transition from thetransition state c to the state D. In addition, the state of the opticalpath shifting element 100 ends the transition to the state D at thetiming t71. Furthermore, the state of the optical path shifting element100 is maintained in the state D in the period from the timing t71 tothe timing t72. Also at the timing t72, the state of the optical pathshifting element 100 starts to transition from the state D to thetransition state d. Furthermore, the state of the optical path shiftingelement 100 ends the transition to the transition state d at the timingt73. Furthermore, the state of the optical path shifting element 100 ismaintained in the transition state d in the period from the timing t73to the timing t74. Also at the timing t74, the state of the optical pathshifting element 100 starts to transition from the transition state d tothe state A. Furthermore, the state of the optical path shifting element100 ends the transition to the state A at the timing t75. Furthermore,the state of the optical path shifting element 100 is maintained in thestate A in the period from the timing t75 to the timing t76. Also at thetiming t76, the state of the optical path shifting element 100 starts totransition from the state A to the transition state a Furthermore, thestate of the optical path shifting element 100 ends the transition tothe transition state a at the timing t77.

As described above, the state of the optical path shifting element 100transitions from the state A to the state A again passing through thetransition state a, the state B, the transition state b, the state C,the transition state c, the state D, and the transition state d.

In the embodiment, the timing control circuit 13 described abovecontrols the amount of change in the state of the optical path shiftingelement 100 in the transition periods described above based on the typeof the image. In more detail, when an image to be expressed with pixelsseparated from each other is to be displayed, the timing control circuit13 changes a position at which light is projected by the optical pathshifting element 100 from the projection position (A) to the projectionposition (B) as an example. On the other hand, when an image withunclear boundaries between pixels is to be displayed, the timing controlcircuit 13 changes a position at which light is projected by the opticalpath shifting element 100 from the projection position (A) to theprojection position (a) or from the projection position (a) to theprojection position (B) as an example. The projector 1 according to theembodiment is capable of controlling the amount of change in the stateof the optical path shifting element 100 in the transition periods inwhich the element transitions from the first unit period f1 to thesecond unit period f2 based on the type of the image, and thus candisplay the image with a desirable pixel interval.

In the embodiment, the timing control circuit 13 controls a state of theoptical path shifting element 100 such that, in the first transitionperiod T1 in which a unit period transitions from the first unit periodf1 to the second unit period f2, light emitted from a predeterminedpixel reaches the projection position (a) that is a third position onthe display screen that differs from the projection position (A) that isa first position on the display screen that the light reaches in thefirst unit period f1 and the projection position (B) that is a secondposition on the display screen that the light reaches in the second unitperiod f2. In particular, in the embodiment, the projection position (a)is a position in the middle of the projection position (A) and theprojection position (B). In the related art, the projection position inthe first unit period f1 is the projection position (A), and when theprojection position in the second unit period f2 is the projectionposition (B). On the other hand, when an image with unclear boundariesbetween pixels is to be displayed in the embodiment, the optical pathshifting element 100 emits light to the projection position (a) in themiddle of the projection position (A) and the projection position (B) asillustrated in FIG. 10 in the transition period in which transition ismade from the first unit period to the second unit period. This allowsthe projector 1 to display the image with unclear boundaries betweenpixels so that the intervals between the pixels are unnoticeable.

In addition, the image processing circuit 11 generates an image signalto be supplied to the liquid crystal panel 10 as an image signal in thetransition period T1 based on the first image signal Vx to be suppliedto the liquid crystal panel 10 in the first unit period f1 and thesecond image signal Vy to be supplied to the liquid crystal panel 10 inthe second unit period f2. Furthermore, the image processing circuit 11sets the output image signal Dr in the transition state a between thestate A in the first unit period f1 and the state B in the second unitperiod f2 as an intermediate signal between the output image signal Drwhile being in the state A and the output image signal Dr while being inthe state B. As a result, when an image with unclear boundaries betweenpixels is to be displayed, the projector 1 can display the image suchthat the intervals of the pixels are unnoticeable.

Third Embodiment

Next, a drive method for a projector 1 according to the third embodimentof the present disclosure will be described with reference to FIGS. 12to 14 . Hereinafter, a difference between the drive method for theprojector 1 according to the third embodiment and the drive method forthe projector 1 according to the first and second embodiments will bemainly described.

Further, it is assumed in the first and second embodiments that oneframe period is divided into four unit periods including the first unitperiod f1, the second unit period f2, a third unit period f3, and afourth unit period f4. Meanwhile, it is assumed in the first and secondembodiments that the first unit period is f2, the second unit period isf4, and the third unit period is f3, and the fourth unit period is f1.In addition, in the first and second embodiments, the projectionposition (A) is set to a “first position”, the projection position (B)is set to a “second position”, and the projection position (a) is set toa “third position” as an example. Meanwhile, in the embodiment, theprojection position (B) is set to a “first position”, the projectionposition (D) is set to a “second position”, the projection position (a)is set to a “third position”, the projection position (C) is set to a“fourth position”, and the projection position (A) is set to a “fifthposition” as an example.

FIG. 12 is a diagram illustrating states of the optical path shiftingelement 100, specifically, projection positions by the optical pathshifting element 100. To be more specific, “A”, “B”, “C”, and “D” on theleft side in both “video odd-numbered frame” and “video even-numberedframe” in FIG. 12 correspond to “A1”, “B1”, “C1”, and “D1” illustratedin FIG. 5 , respectively, as an example. In addition, “A”, “B”, “C”, and“D” on the right side in both “video odd-numbered frame” and “videoeven-numbered frame” in FIG. 12 correspond to “A2”, “B2”, “C2”, and “D2”illustrated in FIG. 5 , respectively, as an example.

FIGS. 13A and 13B are diagrams illustrating a relationship between theprojection positions by the optical path shifting element 100 and thecontrol signals CTL1_X and CTL1_Y over time that is a relationship overtime in display of a natural image. In more detail, FIG. 13A is adiagram illustrating a relationship over time when displaying anodd-numbered frame of a video in display of a natural image. On theother hand, FIG. 13B is a diagram illustrating a relationship over timewhen displaying an even-numbered frame of a video in display of anatural image. Further, in FIGS. 13A and 13B, a highest value of CTL1_Xand CTL1_Y is set to 100V, and a lowest value thereof is set to 0V as anexample. However, an aspect of the embodiment is not limited thereto. Inaddition, because the relationship between the projection positions ofthe optical path shifting element 100 and the control signals CTL1_X andCTL1_Y over time in display of a character drawing is similar to that inthe first embodiment, description thereof will be omitted.

As illustrated in FIG. 12 , when a natural image is to be displayed bythe projector 1, order in which a state of the optical path shiftingelement 100 is switched is made to differ between when an odd-numberedframe of a video is displayed and when an even-numbered frame of thevideo is displayed. Specifically, when an odd-numbered frame of a videois to be displayed, the state of the optical path shifting element 100transitions in order of the state A, the state B, the transition statea, the state D, the state C, the transition state a, the state A, andthe like. On the other hand, when an even-numbered frame of a video isto be displayed, the state of the optical path shifting element 100transitions in order of the state A, the state D, the transition statea, the state B, the state C, the transition state a, the state A, andthe like.

Furthermore, the projection position while the state of the optical pathshifting element 100 is the transition state a is the center of thesquare with four vertexes including the projection position (A), theprojection position (B), the projection position (C), and the projectionposition (D).

Further, when an odd-numbered frame of a video is to be displayed, if animage to be displayed differs between while the state of the opticalpath shifting element 100 is the state B and the state is the state D,an intermediate image of the image displayed while the state of theoptical path shifting element 100 is the transition state B and theimage displayed while the state of the optical path shifting element 100is the state D may be displayed while the state thereof is thetransition state a. Specifically, when the output image signals Dr, Dg,and Db differ between while the state of the optical path shiftingelement 100 is the state B and the state is the state D, the outputimage signal Dr while the state of the optical path shifting element 100is the transition state a may be an intermediate signal of the outputimage signal Dr while the state is the state B and the output imagesignal Dr while the state is the state D. The same applies to the outputimage signals Dg and Db.

Thus, as an example, the image signal Dod for the overdriving while thestate of the optical path shifting element 100 is the transition state athat is between the state B and the state D may be calculated using theabove formula [1] with the low-resolution image signal VIDL in the stateD set as the first image signal Vx and the low-resolution image signalVIDL in the state B set as the second image signal Vy.

Further, when an odd-numbered frame of a video is to be displayed, theoutput image signal Dr in the transition state a that is between thestate C and the state A when an image to be displayed differs betweenwhile the state of the optical path shifting element 100 is the state Cand while the state is the state A is an intermediate signal of theoutput image signal Dr while the element is in the state C and theoutput image signal Dr while the element is in the state A, similarly tothe output image signal Dr in the transition state a that is between thestate B and the state D.

Further, when an even-numbered frame of a video is to be displayed, ifan image to be displayed differs between while the state of the opticalpath shifting element 100 is the state D and the state is the state B,an intermediate image of the image displayed while the state of theoptical path shifting element 100 is the state D and the image displayedwhile the state thereof is the state B may be displayed while the stateis in the transition state a. Specifically, when the output imagesignals Dr, Dg, and Db differ between while the state of the opticalpath shifting element 100 is the state D and the state thereof is thestate B, the output image signal Dr while the state of the optical pathshifting element 100 is the transition state a may be an intermediatesignal of the output image signal Dr while the state is the state D andthe output image signal Dr while the state is the state B. The sameapplies to the output image signals Dg and Db.

Thus, as an example, the image signal Dod for the overdriving while thestate of the optical path shifting element 100 is the transition state athat is between the state D and the state B may be calculated using theabove formula [1] with the low-resolution image signal VIDL in the stateB set as the first image signal Vx and the low-resolution image signalVIDL in the state D set as the second image signal Vy.

Further, when the even-numbered frame of the video is to be displayed,the same applies to the transition state a that is between the state Cand the state A when an image to be displayed differs between while thestate of the optical path shifting element 100 is the state C and whilethe state thereof is the state A.

As illustrated in FIG. 13A, when the determination result by the imagedetermination circuit 11A is a natural image and an odd-numbered frameof a video is to be displayed, the voltage of the control signal CTL1_Xincreases from the lowest value to the highest value in the period froma timing t80 to a timing t81. Furthermore, the voltage of the controlsignal CTL1_X is maintained at the highest value in the period from thetiming t81 to a timing t82. Furthermore, the voltage of the controlsignal CTL1_X decreases from the highest value to the intermediate valuein the period from the timing t82 to a timing t83. Furthermore, thevoltage of the control signal CTL1_X is maintained at the intermediatevalue in the period from the timing t83 to a timing t84. Furthermore,the voltage of the control signal CTL1_X decreases from the intermediatevalue to the lowest value in the period from the timing t84 to a timingt85. Furthermore, the voltage of the control signal CTL1_X is maintainedat the lowest value in the period from the timing t85 to the timing t86.In addition, the voltage of the control signal CTL1_X increases from thelowest value to the highest value in the period from the timing t86 to atiming t87. Furthermore, the voltage of the control signal CTL1_X ismaintained at the highest value in the period from the timing t87 to atiming t88. Furthermore, the voltage of the control signal CTL1_Xdecreases from the highest value to the intermediate value in the periodfrom the timing t86 to a timing t89. Furthermore, the voltage of thecontrol signal CTL1_X is maintained at the intermediate value in theperiod from the timing t89 to a timing t90. Furthermore, the voltage ofthe control signal CTL1_X decreases from the intermediate value to thelowest value in the period from the timing t90 to a timing t91.Furthermore, the voltage of the control signal CTL1_X is maintained atthe lowest value in the period from the timing t91 to the timing t92.

Furthermore, the voltage of the control signal CTL1_Y is maintained atthe lowest value in the period from the timing t80 to the timing t82.Furthermore, the voltage of the control signal CTL1.Y increases from thelowest value to the intermediate value in the period from the timing t82to the timing t83. Furthermore, the voltage of the control signal CTL1_Yis maintained at the intermediate value in the period from the timingt83 to the timing t84. Furthermore, the voltage of the control signalCTL1_Y increases from the intermediate value to the highest value in theperiod from the timing t84 to the timing t85. Furthermore, the voltageof the control signal CTL1_Y is maintained at the highest value in theperiod from the timing t85 to the timing t88. Furthermore, the voltageof the control signal CTL1_Y decreases from the highest value to theintermediate value in the period from the timing t88 to a timing t89.Furthermore, the voltage of the control signal CTL1_Y is maintained atthe intermediate value in the period from the timing t89 to the timingt90. Furthermore, the voltage of the control signal CTL1_Y decreasesfrom the intermediate value to the lowest value in the period from thetiming t90 to a timing t91. Furthermore, the voltage of the controlsignal CTL1_Y is maintained at the lowest value in the period from thetiming t91 to the timing t92.

Thus, the state of the optical path shifting element 100 starts totransition from the state A to the state B at the timing t80. Inaddition, the state of the optical path shifting element 100 ends thetransition to the state B at the timing T81. Furthermore, the state ofthe optical path shifting element 100 is maintained in the state B inthe period from the timing t81 to the timing t82. Also at the timingt82, the state of the optical path shifting element 100 starts totransition from the state B to the transition state a. Furthermore, thestate of the optical path shifting element 100 ends the transition tothe transition state a at the timing t83. Furthermore, the state of theoptical path shifting element 100 is maintained in the transition statea in the period from the timing t83 to the timing t84. Also at thetiming t84, the state of the optical path shifting element 100 starts totransition from the transition state a to the state D. In addition, thestate of the optical path shifting element 100 ends the transition tothe state D at the timing t85. Furthermore, the state of the opticalpath shifting element 100 is maintained in the state D in the periodfrom the timing t85 to the timing t86. Also at the timing t86, the stateof the optical path shifting element 100 starts to transition from thestate D to the state C. In addition, the state of the optical pathshifting element 100 ends the transition to the state C at the timingt87. Furthermore, the state of the optical path shifting element 100 ismaintained in the state C in the period from the timing t87 to thetiming t88. Also at the timing t88, the state of the optical pathshifting element 100 starts to transition from the state C to thetransition state a. Furthermore, the state of the optical path shiftingelement 100 ends the transition to the transition state a at the timingt89. Furthermore, the state of the optical path shifting element 100 ismaintained in the transition state a in the period from the timing t89to the timing t90. Also at the timing t90, the state of the optical pathshifting element 100 starts to transition from the transition state a tothe state A. In addition, the state of the optical path shifting element100 ends the transition to the state A at the timing t91. Furthermore,the state of the optical path shifting element 100 is maintained in thestate A in the period from the timing t91 to the timing t92. Also at thetiming t92, the state of the optical path shifting element 100 starts totransition from the state A to the state B.

As described above, the state of the optical path shifting element 100transitions from the state A to the state A again passing through thestate B, the transition state a, the state D, the state C, and thetransition state a.

As illustrated in FIG. 13B, when the determination result by the imagedetermination circuit 11A is a natural image and an even-numbered frameof a video is to be displayed, the voltage of the control signal CTL1_Xis maintained at the lowest value in the period from a timing t100 to atiming t102. Furthermore, the voltage of the control signal CTL1_Xincreases from the lowest value to the intermediate value in the periodfrom the timing t102 to a timing t103. Furthermore, the voltage of thecontrol signal CTL1_X is maintained at the intermediate value in theperiod from the timing t103 to a timing t104. Furthermore, the voltageof the control signal CTL1_X increases from the intermediate value tothe highest value in the period from the timing t104 to a timing t105.Furthermore, the voltage of the control signal CTL1_X is maintained atthe highest value in the period from the timing t105 to a timing t108.Furthermore, the voltage of the control signal CTL1_X decreases from thehighest value to the intermediate value in the period from the timingt108 to a timing t109. Furthermore, the voltage of the control signalCTL1_X is maintained at the intermediate value in the period from thetiming t109 to a timing t110. Furthermore, the voltage of the controlsignal CTL1_X decreases from the intermediate value to the lowest valuein the period from the timing t110 to a timing t111. Furthermore, thevoltage of the control signal CTL1_X is maintained at the lowest valuein the period from the timing t111 to a timing t112.

Furthermore, the voltage of the control signal CTL1_Y increases from thelowest value to the highest value in the period from the timing t100 toa timing t101. Furthermore, the voltage of the control signal CTL1_Y ismaintained at the highest value in the period from the timing t101 tothe timing t102. Furthermore, the voltage of the control signal CTL1_Ydecreases from the highest value to the intermediate value in the periodfrom the timing t102 to the timing t103. Furthermore, the voltage of thecontrol signal CTL1_Y is maintained at the intermediate value in theperiod from the timing t103 to the timing t104. Furthermore, the voltageof the control signal CTL1_Y decreases from the intermediate value tothe lowest value in the period from the timing t104 to the timing t105.Furthermore, the voltage of the control signal CTL1_Y is maintained atthe lowest value in the period from the timing t105 to a timing t106. Inaddition, the voltage of the control signal CTL1_Y increases from thelowest value to the highest value in the period from the timing t106 tothe timing t107. Furthermore, the voltage of the control signal CTL1_Yis maintained at the highest value in the period from the timing t107 tothe timing t108. Furthermore, the voltage of the control signal CTL1_Ydecreases from the highest value to the intermediate value in the periodfrom the timing t108 to the timing t109. Furthermore, the voltage of thecontrol signal CTL1_Y is maintained at the intermediate value in theperiod from the timing t109 to the timing t110. Furthermore, the voltageof the control signal CTL1_Y decreases from the intermediate value tothe lowest value in the period from the timing t110 to the timing t111.Furthermore, the voltage of the control signal CTL1_Y is maintained atthe lowest value in the period from the timing t111 to the timing t112.

Thus, the state of the optical path shifting element 100 starts totransition from the state A to the state D at the timing t100. Inaddition, the state of the optical path shifting element 100 ends thetransition to the state D at the timing t101. Furthermore, the state ofthe optical path shifting element 100 is maintained in the state D inthe period from the timing t101 to the timing t102. Also at the timingt102, the state of the optical path shifting element 100 starts totransition from the state D to the transition state a. Furthermore, thestate of the optical path shifting element 100 ends the transition tothe transition state a at the timing t103. Furthermore, the state of theoptical path shifting element 100 is maintained in the transition statea in the period from the timing t103 to the timing t104. Also at thetiming t104, the state of the optical path shifting element 100 startsto transition from the transition state a to the state B. In addition,the state of the optical path shifting element 100 ends the transitionto the state B at the timing t105. Furthermore, the state of the opticalpath shifting element 100 is maintained in the state B in the periodfrom the timing t105 to the timing t106. Also at the timing t106, thestate of the optical path shifting element 100 starts to transition fromthe state B to the state C. In addition, the state of the optical pathshifting element 100 ends the transition to the state C at the timingt107. Furthermore, the state of the optical path shifting element 100 ismaintained in the state C in the period from the timing t107 to thetiming t108. Also at the timing t108, the state of the optical pathshifting element 100 starts to transition from the state C to thetransition state a. Furthermore, the state of the optical path shiftingelement 100 ends the transition to the transition state a at the timingt109. Furthermore, the state of the optical path shifting element 100 ismaintained in the transition state a in the period from the timing t109to the timing t110. Also at the timing t110, the state of the opticalpath shifting element 100 starts to transition from the transition statea to the state A. In addition, the state of the optical path shiftingelement 100 ends the transition to the state A at the timing t111.Furthermore, the state of the optical path shifting element 100 ismaintained in the state A in the period from the timing t111 to thetiming t112. Also at the timing t112, the state of the optical pathshifting element 100 starts to transition from the state A to the stateB.

As described above, the state of the optical path shifting element 100transitions from the state A to the state A again passing through thestate D, the transition state a, the state B, the state C, and thetransition state a.

In the embodiment, when pixels to be displayed move in the horizontaldirection and the vertical direction, the transition time is shorterlike, for example, the time from t80 to t81, and when pixels to bedisplayed move in a diagonal direction, the transition time is longerlike, for example, the time from t82 to t85 as illustrated in FIGS. 13Aand 13B. Further, the voltage of the control signal CTL1_X or CTL1_Y ismaintained at the intermediate value in the latter transition time. Thismakes it possible to eliminate display rattling by artfully increasingthe amount of information when displaying a diagonal line.

FIG. 14 illustrates a display example as a comparative example and adisplay example of a display method according to the embodiment. In FIG.14 , the display example of the comparative example illustrated in FIG.7 is illustrated as well to make it easier to understand the displaymethod according to the embodiment. More specifically, in the upperportion of FIG. 14 , a display example of a vertical line, a horizontalline, and diagonal lines according to a method of the related art isillustrated as the comparative example. In addition, in the lowerportion of FIG. 14 , a display example of a vertical line, a horizontalline, and diagonal lines according to the display method according tothe embodiment is illustrated. Comparing the display example as thecomparative example to the display example of the display methodaccording to the embodiment, there is no difference between the examplesin the display of the vertical lines and the horizontal lines. However,in the display of the diagonal lines according to the embodiment, imagescorresponding to the transition state a between the state B and thestate D and the transition state a between the state A and the state Care displayed in addition to the image displayed in the method of therelated art. This lowers the degree of display rattling. Further, inFIG. 14 , the image corresponding to the transition state a is indicatedby a coarse lattice.

In the embodiment, in a transition period, the projection position bythe optical path shifting element 100 is at the center of the squarehaving, as four vertexes, the projection position (B) that is the firstposition that the projection position reaches in the first unit periodf2, the projection position (D) that is the second position that theprojection position reaches at the second unit period f4, the projectionposition (C) that is the third position that the projection positionreaches in the third unit period f3, and the projection position (A)that is the fourth position that the projection position reaches in thefourth unit period f1. In addition, when the position to be reachedmoves on the display screen of light emitted from a predetermined pixelfrom the first unit period f2 to the fourth unit, period f1, and whenthe position moves in the horizontal direction and the verticaldirection, the transition time is shorter, and on the other hand, whenthe position moves in the diagonal direction, the transition time islonger. This makes it possible to lower the degree of display rattlingwhen displaying diagonal lines.

Furthermore, in the embodiment, depending on whether an odd-numberedframe or an even-numbered frame of a video is to be displayed, movementof the projection position by the optical path shifting element 100 isswitched to a combined direction of the horizontal direction and thediagonal direction or a combined direction of the vertical direction andthe diagonal direction. The reason for this is that, when the projectionposition by the optical path shifting element 100 moves only in thecombined direction of the horizontal direction and the diagonaldirection or the combined direction of the vertical direction and thediagonal direction, asymmetry occurs in the movement direction. Thus,if, as the movement direction of the projection position by the opticalpath shifting element 100, balance is taken between the combineddirection of the horizontal direction and the diagonal direction and thecombined direction of the vertical direction and the diagonal direction,symmetry in the movement direction can be maintained. In addition, ifall movement directions including the horizontal direction, the verticaldirection, and the diagonal direction are mixed for the movementdirection of the projection position, and the movement direction isaveraged, dot display becomes smoother.

Fourth Embodiment

Next, a drive method for the projector 1 according to a fourthembodiment of the present disclosure will be described with reference toFIGS. 15 and 16 . Hereinafter, a difference between the drive method forthe projector 1 according to the fourth embodiment and the drive methodfor the projector 1 according to the first to third embodiments will bemainly described.

FIG. 15 is a diagram illustrating states of the optical path shiftingelement 100, specifically, projection positions by the optical pathshifting element 100. To be more specific, “A”, “B”, “C”, and “D” on theleft side in FIG. 15 correspond to “A1”, “B1”, “C1”, and “D1”illustratedin FIG. 5 , respectively, as an example. In addition, “A”, “B”, “C”, and“D” on the right side in FIG. 15 correspond to “A2”, “B2”, “C2”, and“D2” illustrated in FIG. 5 , respectively, as an example.

FIG. 16 is a diagram illustrating a relationship between a projectionposition by the optical path shifting element 100 and control signalsCTL1_X and CTL1_Y over time. Further, FIG. 16 shows a highest value ofCTL1_X and CTL1_Y at 100V, a lowest value thereof at 0V, and anintermediate value at 50V as an example. However, an aspect of theembodiment is not limited thereto.

Comparing FIG. 15 to FIG. 10 illustrating the projection positions bythe optical path shifting element 100 according to the secondembodiment, the projection positions while the element is in thetransition states a to d are the midpoint of the projection position (A)and the projection position (B), the midpoint of the projection position(B) and the projection position (C), the midpoint of the projectionposition (C) and the projection position (D), and the midpoint of theprojection position (D) and the projection position (A) in the secondembodiment. On the other hand, in the embodiment, the projectionposition (a) while the element is in the transition state a is theposition between the midpoint P of the projection position (A) and theprojection position (B) and the center O of the square having the fourvertexes including the projection position (A), the projection position(B), the projection position (C), and the projection position (D).Similarly, the projection position (b) while the element is in thetransition state b is the position between the midpoint Q of theprojection position (B) and the projection position (C) and the center Oof the square. Similarly, the projection positon (c) while the elementis in the transition state c is the position between the midpoint R ofthe projection position (C) and the projection position (D) and thecenter O of the square. Similarly, the projection position (d) while theelement is in the transition state d is the position between themidpoint S of the projection position (D) and the projection position(A) and the center O of the square.

Thus, the image shift state transitions to the state A, the transitionstate a, state B, the transition state b, state C, the transition statec, state D, the transition state d, state A, and the like, but theprojection position by the optical path shifting element 100 is alwaysmoved obliquely.

As described above, for example, the projection position while the stateof the optical path shifting element 100 is in the transition state a isa position closer to the center of the square having the four vertexesincluding the projection position (A), the projection position (B), theprojection position (C), and the projection position (D) than to themidpoint of the projection position (A) and the projection position (B).Thus, if an image to be displayed differs while the state of the opticalpath shifting element 100 is each of the state A to the state D, theintermediate image of the image to be displayed while the state of theoptical path shifting element 100 is the transition state a and theimage to be displayed while the state of the optical path shiftingelement 100 is the state A to the state D may be displayed. Further, theintermediate image may be generated by weighing each of the images to bedisplayed while the element is in each of the state A to the state D.

Although the operation performed while the state of the optical pathshifting element 100 is the transition state a has been described above,the projector 1 performs similar operations while the state of theoptical path shifting element 100 is one of the transition states b tod.

Thus, as an example, the image signal Dod for overdriving while thestate of the optical path shifting element 100 is the transition state amay be given using the following formula [2] after setting thelow-resolution image signal VIDL when the element is in the state A to asecond image signal V_(A), the low-resolution image signal VIDL when theelement is in the state B to a first image signal V_(B), thelow-resolution image signal VIDL when the element is in the state C to afirst image signal V_(C), the low-resolution image signal VIDL when theelement is in the state D to a first image signal V_(D).

Dod =f₂ (V_(A), V_(B), V_(C), V_(D))   [2]

Further, the function f₂ is determined to obtain a desired grayscaleconsidering response characteristics of the liquid crystal, like thefunction f₁. This compensates for the response characteristics of theliquid crystal panel 10.

When the determination result by the image determination circuit 11A isa natural image, the voltage of the control signal CTL1_X increases fromthe lowest value to an intermediate value in the period from a timingt120 to a timing t121 as illustrated in FIG. 16 . Furthermore, thevoltage of the control signal CTL1_X is maintained at the intermediatevalue in the period from the timing t121 to a timing t122. Furthermore,the voltage of the control signal CTL1_X increases from the intermediatevalue to the highest value in the period from the timing t122 to atiming t123. Furthermore, the voltage of the control signal CTL1_X ismaintained at the highest value in the period from the timing t123 to atiming t124. Furthermore, the voltage of the control signal CTL1_Xdecreases from the highest value to the intermediate value in the periodfrom the timing t124 to a timing t125. Furthermore, the voltage of thecontrol signal CTL1_X is maintained at the intermediate value in theperiod from the timing t125 to a timing t126 Furthermore, the voltage ofthe control signal CTL1_X increases from the intermediate value to thehighest value in the period from the timing t126 to a timing t127.Furthermore, the voltage of the control signal CTL1_X is maintained atthe highest value in the period from the timing t127 to a timing t128.Furthermore, the voltage of the control signal CTL1_X decreases from thehighest value to the intermediate value in the period from the timingt128 to a timing t129. Furthermore, the voltage of the control signalCTL1_X is maintained at the intermediate value in the period from thetiming t129 to a timing t130. Furthermore, the voltage of the controlsignal CTL1_X decreases from the intermediate value to the lowest valuein the period from the timing t130 to a timing t131. Furthermore, thevoltage of the control signal CTL1_X is maintained at the lowest valuein the period from the timing t131 to a timing t136. Furthermore, thevoltage of the control signal CTL1_X increases from the lowest value tothe intermediate value in the period from the timing t136 to a timingt137.

Furthermore, the voltage of the control signal CTL1_Y increases from thelowest value to the intermediate value in the period from the timingt120 to the timing t121. Furthermore, the voltage of the control signalCTL1_Y is maintained at the intermediate value in the period from thetiming t121 to the timing t122. Furthermore, the voltage of the controlsignal CTL1_Y decreases from the intermediate value to the lowest valuein the period from the timing t122 to the timing t123. Furthermore, thevoltage of the control signal CTL1_Y is maintained at the lowest valuein the period from the timing t123 to the timing t124. Furthermore, thevoltage of the control signal CTL1_Y increases from the lowest value tothe intermediate value in the period from the timing t124 to the timingt125. Furthermore, the voltage of the control signal CTL1_Y ismaintained at the intermediate value in the period from the timing t125to the timing t126. Furthermore, the voltage of the control signalCTL1_Y increases from the intermediate value to the highest value in theperiod from the timing t126 to the timing t127. Furthermore, the voltageof the control signal CTL1_Y is maintained at the highest value in theperiod. from the timing t127 to a timing t132. Furthermore, the voltageof the control signal CTL1_Y decreases from the highest value to theintermediate value in the period from the timing t132 to a timing t133.Furthermore, the voltage of the control signal CTL1_Y is maintained atthe intermediate value in the period from the timing t133 to a timingt134. Furthermore, the voltage of the control signal CTL1_Y decreasesfrom the intermediate value to the lowest value in the period from thetiming t134 to a timing t135. Furthermore, the voltage of the controlsignal CTL1_Y is maintained at the lowest value in the period from thetiming t135 to the timing t136. Furthermore, the voltage of the controlsignal CTL1_Y increases from the lowest value to the intermediate valuein the period from the timing t136 to the timing t137.

Thus, the state of the optical path shifting element 100 starts totransition from the state A to the transition state a at the timingt120. Furthermore, the state of the optical path shifting element 100ends the transition to the transition state a at the timing t121.Furthermore, the state of the optical path shifting element 100 ismaintained in the transition state a in the period from the timing t121to the timing t122. Also at the timing t122, the state of the opticalpath shifting element 100 starts to transition from the transition statea to the state B. In addition, the state of the optical path shiftingelement 100 ends the transition to the state B at the timing t123.Furthermore, the state of the optical path shifting element 100 ismaintained in the state B in the period from the timing t123 to thetiming t124. Also at the timing t124, the state of the optical pathshifting element 100 starts to transition from the state B to thetransition state b. Furthermore, the state of the optical path shiftingelement 100 ends the transition to the transition state b at the timingt125. Furthermore, the state of the optical path shifting element 100 ismaintained in the transition state b in the period from the timing t125to the timing t126. Also at the timing t126, the state of the opticalpath shifting element 100 starts to transition from the transition stateb to the state C. In addition, the state of the optical path shiftingelement 100 ends the transition to the state C at the timing t127.Furthermore, the state of the optical path shifting element 100 ismaintained in the state C in the period from the timing t127 to thetiming t128. Also at the timing t128, the state of the optical pathshifting element 100 starts to transition from the state C to thetransition state c. Furthermore, the state of the optical path shiftingelement 100 ends the transition to the transition state c at the timingt129. Furthermore, the state of the optical path shifting element 100 ismaintained in the transition state c in the period from the timing t129to the timing t130. Also at the timing t130, the state of the opticalpath shifting element 100 starts to transition from the transition statec to the state D. In addition, the state of the optical path shiftingelement 100 ends the transition to the state D at the timing t131.Furthermore, the state of the optical path shifting element 100 ismaintained in the state D in the period from the timing t131 to thetiming t132. Also at the timing t132, the state of the optical pathshifting element 100 starts to transition from the state D to thetransition state d. In addition, the state of the optical path shiftingelement 100 ends the transition to the transition state d at the timingt133. Furthermore, the state of the optical path shifting element 100 ismaintained in the transition state d in the period from the timing t133to the timing t134. Also at the timing t134, the state of the opticalpath shifting element 100 starts to transition from the transition stated to the state A. In addition, the state of the optical path shiftingelement 100 ends the transition to the state A at the timing t135.Furthermore, the state of the optical path shifting element 100 ismaintained in the state A in the period from the timing t135 to thetiming t136. Also at the timing t136, the state of the optical pathshifting element 100 starts to transition from the state A to thetransition state a. Furthermore, the state of the optical path shiftingelement 100 ends the transition to the transition state a at the timingt137.

As described above, the state of the optical path shifting element 100transitions from the state A to the state A again passing through thetransition state a, the state B, the transition state b, the state C,the transition state c, the state D, and the transition state d.

In the embodiment, the projection position by the optical path shiftingelement 100 moves in a diagonal direction at all times. This makes itpossible to lower the degree of display rattling when displayingdiagonal lines as in the third embodiment.

Fifth Embodiment

Next, a drive method for the projector 1 according to a fifth embodimentof the present disclosure will be described with reference to FIGS. 17Aand 17B. Hereinafter, a difference between the drive method for theprojector 1 according to the fifth embodiment and the drive method forthe projector 1 according to the first to fourth embodiments will bemainly described.

FIGS. 17A and 17B are diagrams illustrating states of the optical pathshifting element 100, specifically, projection positions by the opticalpath shifting element 100. To be more specific, “A”, “B”, “C”, and “D”on the left side in FIG. 17A correspond to “A1”, “B1”, “C1”, and “D1”illustrated in FIG. 5 , respectively, as an example. In addition, “A”,“B”, “C”, and “D” on the right side in FIG. 17A correspond to “A2”,“B2”, “C2”, and “D2” illustrated in FIG. 5 , respectively, as anexample. In addition, “A”, “B”, “C”, and “D” on the upper left side inFIG. 17B correspond to “A1”, “B1”, “C1”, and “D1” illustrated in FIG. 5, respectively, as an example. In addition, “A”, “B”, “C”, and “D” onthe upper right side in FIG. 17B correspond to “A2”, “B2”, “C2”, and“D2” illustrated in FIG. 5 , respectively, as an example. In addition,“A”, “B”, “C”, and “D” on the lower left side in FIG. 17B correspond to“A4”, “B4”, “C4”, and “D4” illustrated in FIG. 5 , respectively, as anexample. In addition, “A”, “B”, “C”, and “D” on the lower right side inFIG. 17B correspond to “A5”, “B5”, “C5”, and “D5” illustrated in FIG. 5, respectively, as an example.

As illustrated in FIGS. 17A and 17B in the embodiment, when a naturalimage is to be displayed by the projector 1, the projection positionwhen a state of the optical path shifting element 100 is a transitionstate is switched when an odd-numbered frame of a video is displayed andwhen an even-numbered frame of the video is displayed. Further, order inwhich the state of the optical path shifting element 100 transitions isthe same when an odd-numbered frame of a video is displayed and when aneven-numbered frame of the video is displayed. Specifically, the stateof the optical path shifting element 100 transitions in order of thestate A, the transition state a, the state B, the transition state b,the state C, the transition state c, the state D, the transition stated, the state A, and so on.

When an odd-numbered frame of a video is displayed, the projectionposition (a) by the optical path shifting element 100 while the state ofthe optical path shifting element 100 is the transition state a is aposition between a midpoint P of the projection position (A) and theprojection position (B) and the center O₁ of the square having fourvertexes including the projection position (A), the projection position(B), the projection position (C), and the projection position (D) inorder clockwise from the upper left side as illustrated in FIG. 17A. Theprojection position (b) by the optical path shifting element 100 whilethe state of the optical path shifting element 100 is in the transitionstate b is a position between a midpoint Q between the projectionposition (B) and the projection position (C) and the center O₂ of thesquare having the four vertexes including the projection position (B),the projection position (A), the projection position (D), and theprojection position (C) in order clockwise from the upper left side. Theprojection position (c) by the optical path shifting element 100 whilethe state of the optical path shifting element 100 is the transitionstate c is a position between a midpoint R of the projection position(C) and the projection position (D) and the center O₁ of the square. Theprojection position (d) by the optical path shifting element 100 whilethe state of the optical path shifting element 100 is in the transitionstate d is a position between a midpoint S between the projectionposition (D) and the projection position (A) and the center O₃ of thesquare having the four vertexes including the projection position (B),the projection position (A), the projection position (D), and theprojection position (C) in order clockwise from the upper left side.That is, when the odd-numbered frame of the video is displayed, atrajectory is drawn on the projection positions in the form of a lyingnumber 8.

On the other hand, when an even-numbered frame of a video is displayed,the projection position (a) by the optical path shifting element 100while the state of the optical path shifting element 100 is thetransition state a is a position between a midpoint P of the projectionposition (A) and the projection position (B) and the center O₄ of thesquare having four vertexes including the projection position (D), theprojection position (C), the projection position (B), and the projectionposition (A) in order clockwise from the upper left side as illustratedin FIG. 17B. The projection position (b) by the optical path shiftingelement 100 while the state of the optical path shifting element 100 isthe transition state b is a position between a midpoint Q of theprojection position (B) and the projection position (C) and the centerO₁ of the square. The projection position (c) by the optical pathshifting element 100 while the state of the optical path shiftingelement 100 is the transition state c is a position between a midpoint Rbetween the projection position (C) and the projection position (D) andthe center O₅ of the square having the four vertexes including theprojection position (D), the projection position (C), the projectionposition (B), and the projection position (A) in order clockwise fromthe upper left side. The projection position (d) by the optical pathshifting element 100 while the state of the optical path shiftingelement 100 is the transition state d is a position between a midpoint Sof the projection position (D) and the projection position (A) and thecenter O₁ of the square. That is, when the odd-numbered frame of thevideo is displayed, a trajectory is drawn on the projection positions inthe form of standing number 8.

In the embodiment, the projection position of the optical path shiftingelement 100 moves in the diagonal direction at all times, as in thefourth embodiment. This makes it possible to eliminate display rattlingwhen displaying diagonal lines, as in the third and fourth embodiments.

In addition, in the embodiment, the trajectory of the projectionpositions switches to the trajectory in the form of a lying number 8 orthe trajectory in the form of a standing number 8 depending on whetherthe video to be displayed is of an odd-numbered frame or aneven-numbered frame. The reason for this is that asymmetry occurs in themoving direction when the trajectory of the projection positions is onlyset to the trajectory in the form of a lying number 8 or when thetrajectory thereof is only set to the trajectory in the form of astanding number 8. As a result, by generating the trajectory in the formof a lying number 8 and the trajectory in the form of a standing number8 as the trajectory of the projection positions in a well-balancedmanner, symmetry in the movement direction can be maintained. Inaddition, the trajectory of the projection positions is averaged, anddot display becomes smoother.

Sixth Embodiment

Next, a drive method for a projector 1 according to a sixth embodimentof the present disclosure will be described with reference to FIG. 18 .Hereinafter, a difference between an operation of the projector 1according to the sixth embodiment and the operation of the projector 1according to the first to fifth embodiments will be mainly described.

FIG. 18 is a diagram illustrating states of an optical path shiftingelement 100, specifically, projection positions by the optical pathshifting element 100. To be more specific, “A”, “B”, “C”, and “D” on theleft side in FIG. 18 correspond to “A1”, “B1”, “C1”, and “D1”illustrated in FIG. 5 , respectively, as an example. In addition, “A”,“B”, “C”, and “D” on the right side in FIG. 18 correspond to “A2”, “B2”,“C2”, and “D2” illustrated in FIG. 5 , respectively, as an example.

When a natural image is displayed by the projector 1 in the embodiment,a projection position while the state of the optical path shiftingelement 100 is a transition state is switched as illustrated in FIG. 18according to the time that has elapsed after the projector 1 startedimage display.

Specifically, in the embodiment, a state of the optical path shiftingelement 100 transitions to the state A, a transition state a₁, the stateB, a transition state b₁, the state C, a transition state c₁, the stateD, a transition state d₁, the state A, a transition State a₂, the stateB, a transition state b₂, the state C, a transition state c₂, the stateD, a transition state d₂, the state A, and the like in order.Hereinafter, a period in which a state of the optical path shiftingelement 100 transitions to the state A, the transition state a₁, thestate B, the transition state b₁, the state C, the transition state C₁,the state D, and the transition state d₁ in order will be referred to asa first subframe period. In addition, a period in which a state of theoptical path shifting element 100 transitions to the state A, thetransition state a₂, the state B, the transition state b₂, the state C,the transition state c₂, the state D, and the transition state d₂ inorder will be referred to as a second subframe period below.

Further, one frame period may be constituted by the first subframeperiod and the second subframe period described above, or one frameperiod may be only the first subframe period described above, or onlythe second subframe period described above.

In addition, a projection position (a₁) by the optical path shiftingelement 100 while a state of the optical path shifting element 100 isthe transition state a₁ is a position between a midpoint P of theprojection position (A) and the projection position (B) and the centerO₁ of the square having the four vertexes including the projectionposition (A), the projection position (B), the projection position (C),and the projection position (D) in order clockwise from the upper leftside. Meanwhile, a projection position (a₂) by the optical path shiftingelement 100 while a state of the optical path shifting element 100 isthe transition state a₂ is a position between the midpoint P of theprojection position (A) and the projection position (B) and the centerO₄ of the square having the four vertexes including the projectionposition (D), the projection position (C), the projection position (B),and the projection position (A) in order clockwise from the upper leftside.

Likewise, a projection position (b₁) by the optical path shiftingelement 100 while the state of the optical path shifting element 100 isin the transition state b₁ is a position between a midpoint Q betweenthe projection position (B) and the projection position (C) and thecenter O₂ of the square having the four vertexes including theprojection position (B), the projection position (A), the projectionposition (D), and the projection position (C) in order clockwise fromthe upper left side. Meanwhile, a projection position (b₂) by theoptical path shifting element 100 while a state of the optical pathshifting element 100 is the transition state b₂ is a position betweenthe midpoint Q of the projection position (B) and the projectionposition (C) and the center O₁ of the square having the four vertexesincluding the projection position (A), the projection position (B), theprojection position (C), and the projection position (D) in orderclockwise from the upper left side.

Likewise, a projection position (c₁) by the optical path shiftingelement 100 while a state of the optical path shifting element 100 isthe transition state c₁ is a position between a midpoint R of theprojection position (C) and the projection position (D) and the centerO₁ of the square having the four vertexes including the projectionposition (A), the projection position (B), the projection position (C),and the projection position (D) in order clockwise from the upper leftside. Meanwhile, a projection position (c₂) by the optical path shiftingelement 100 while a state of the optical path shifting element 100 isthe transition state c₂ is a position between the midpoint R between theprojection position (C) and the projection position (D) and the centerO₅ of the square having the four vertexes including the projectionposition (D), the projection position (C), the projection position (B),and the projection position (A) in order clockwise from the upper leftside.

Likewise, a projection position (d₁) by the optical path shiftingelement 100 while a state of the optical path shifting element 100 is atransition state d₁ is a position between a midpoint S between theprojection position (D) and the projection position (A) and the centerO₂ of the square having the four vertexes including the projectionposition (B), the projection position (A), the projection position (D),and the projection position (C) in order clockwise from the upper leftside. Meanwhile, a projection position (d₂) by the optical path shiftingelement 100 while a state of the optical path shifting element 100 isthe transition state d₂ is a position between the midpoint S of theprojection position (D) and the projection position (A) and the centerO₁ of the square having the four vertexes including the projectionposition (A), the projection position (B), the projection position (C),and the projection position (D) in order clockwise from the upper leftside.

Further, in each of the transition states a to d, the projectionposition in the first subframe period and the projection position in thesecond subframe period may be switched therebetween. For example, whilethe projection position by the optical path shifting element 100 whilethe element is in the transition state a may be the position a₂ in FIG.18 in the first subframe period, and may be the position a₁ in FIG. 18in the second subframe period.

As an example, the projection position by the optical path shiftingelement 100 may draw, in the first subframe period, the same trajectoryas that when an odd-numbered frame of a video is displayed in the fifthembodiment, and may draw, in the second subframe period, the sametrajectory as that when an even-numbered frame of a video is displayedin the fifth embodiment.

In the embodiment, the projection position by the optical path shiftingelement 100 moves in the diagonal direction at all times, as in thefourth and fifth embodiments. This makes it possible to lower the degreeof display rattling when displaying diagonal lines as in the third tofifth embodiments.

In addition, in the embodiment, the trajectory of the projectionpositions by the optical path shifting element 100 is switched accordingto the time that has elapsed after the projector 1 started imagedisplay. Thus, the projection positions are averaged, and dot displaybecomes smoother.

Seventh Embodiment

Next, a drive method for a projector 1 according to a seventh embodimentof the present disclosure will be described with reference to FIG. 19 .Hereinafter, a difference between the drive method for the projector 1according to the seventh embodiment and the drive method for theprojector 1 according to the first to sixth embodiments will be mainlydescribed.

FIG. 19 is a diagram illustrating states of an optical path shiftingelement 100, specifically, projection positions by the optical pathshifting element 100. To be more specific, “A”, “B”, “C”, and “D” on theleft side in FIG. 19 correspond to “A1”, “B1”, “C1”, and “D1”illustrated in FIG. 5 , respectively, as an example. In addition, “A”,“B”, “C”, and “D” on the right side in FIG. 19 correspond to “A2”, “B2”,“C2”, and “D2” illustrated in FIG. 5 , respectively, as an example.

Comparing a projection position by the optical path shifting element 100according to the embodiment to the projection position of the opticalpath shifting element 100 according to the second embodiment illustratedin FIG. 10 , all of the protection position (A) to the projectionposition (D) move away from the center O₁ of the square having the fourvertexes including the projection position (A) to the projectionposition (D) of the second embodiment. More particularly, the projectionposition (A) has moved from the center O₁ of the square to the upperleft. The projection position (B) has moved from the center O₁ of thesquare to the upper right. The projection position (C) has moved fromthe center O₁ of the square to the lower left. The projection position(D) has moved from the center O₁ of the square to the lower left.

In the embodiment, by moving the projection position (A) to theprojection position (D) away from the center O₁ of the square, theprojection positions by the optical path shifting element 100 move indiagonal directions at all times, as in the fourth to sixth embodiments.This makes it possible to lower the degree of display rattling whendisplaying diagonal lines as in the third to sixth embodiments. Further,although the projection positions (A) to (D) in the embodiment areassumed to move away from the center O₁ of the square in the abovedescription, compared to the projection positions (A) to (D) by theoptical path shifting element 100 according to the second embodiment, anaspect of the embodiment is not limited thereto. For example, in theembodiment, the projection positions (A) to (D) may move away from thecenter O or any one of the centers O₁ to O₅ of the square, compared tothe projection positions (A) to (D) by the optical path shifting element100 according to the third to sixth embodiments.

MODIFICATION EXAMPLE

The disclosure is not limited to the embodiments illustrated above.Specific modification modes are exemplified below. Two or more modesfreely selected from the examples described below may be combined.

Modification Example 1

Each of the projectors 1 according to the first to seventh embodimentsdescribed above includes, for example, the optical path shifting element100 and the optical path shifting element drive circuit 12. However, theembodiments of the present disclosure are not limited thereto. Forexample, the embodiments of the present disclosure may include a digitalmicro-mirror device (DMD) and a drive circuit thereof in place of theoptical path shifting element 100 and the optical path shifting elementdrive circuit 12.

Modification Example 2

In the first to seventh embodiments described above, for example, VAliquid crystals are provided between the pixel electrodes and thecounter electrodes. However, the embodiments of the present disclosureare not limited thereto. For example, another reflective liquid crystal,or TN or IPS liquid crystals may be provided between the pixelelectrodes and the counter electrodes.

Modification Example 3

In the first to seventh embodiments described above, the timing controlcircuit 13 time-divides a single frame period corresponding to one frameinto unit periods each corresponding to a state of the optical pathshifting element 100. However, the embodiments of the present disclosureare not limited. thereto. For example, the constituent elements of theprojector 1 to 1F, most of all, the constituent elements constitutingthe control system of the projectors 1, may cooperate with each other totime-divide a single frame period corresponding to one frame into unitperiods each corresponding to a state of the optical path shiftingelement 100.

Modification Example 4

When an odd-numbered frame of a video is displayed in the thirdembodiment described above, the projection position by the optical pathshifting element 100 moves in a combined direction of the horizontaldirection and the diagonal direction. On the other hand, when aneven-numbered frame of a video is displayed, the projection position bythe optical path shifting element 100 moves in a combined direction ofthe vertical direction and the diagonal direction. However, theembodiment of the present disclosure is not limited thereto. Forexample, regardless of whether an odd-numbered frame of a video isdisplayed or an even-numbered frame of a video is displayed, theprojection position by the optical path shifting element 100 may move ina combined direction of the horizontal direction and the diagonaldirection. For example, regardless of whether an odd-numbered frame of avideo is displayed or an even-numbered frame of a video is displayed,the projection position by the optical path shifting element 100 maymove in a combined direction of the vertical direction and the diagonaldirection.

What is clamed is:
 1. A projector comprising: an electro-optical panelin which a plurality of pixels are arrayed; an optical path shiftingelement configured to change an optical path of light emitted from theplurality of pixels; an image processing circuit configured to supply afirst image signal based on an input image signal to the electro-opticalpanel in a first unit period among a plurality of unit periods includedin one frame period and supply a second image signal based on the inputimage signal to the electro-optical panel in a second unit period afterthe first unit period among the plurality of unit periods; and a controlcircuit configured to control a state of the optical path shiftingelement such that light emitted from a predetermined pixel among theplurality of pixels reaches a first position on a display screen in thefirst unit period, control a state of the optical path shifting elementsuch that light emitted from the predetermined pixel reaches a secondposition on the display screen in the second unit period, and control,based on a type of image indicated by the input image signal, a state ofthe optical path shifting element in a transition period in which a unitperiod transitions from the first unit period to the second unit period.2. The projector according to claim 1, wherein the control circuitcontrols, based on the type of the image, at least one of a speed ofchange and an amount of change of the state of the optical path shiftingelement in the transition period.
 3. The projector according to claim 1,wherein the image processing circuit includes an overdrive processingcircuit configured to perform overdrive processing to determine acompensation amount for compensating response characteristics of theelectro-optical panel based on a grayscale indicated by the first imagesignal and a grayscale indicated by the second image signal, and theoverdrive processing circuit adjusts the compensation amount determinedin the overdrive processing based on the type of the image.
 4. Theprojector according to claim 1, wherein the control circuit controls astate of the optical path shifting element such that light emitted fromthe predetermined pixel reaches a third position on the display screenin the transition period.
 5. The projector according to claim 4, whereinthe image processing circuit generates a third image signal to besupplied to the electro-optical panel based on the first image signaland the second image signal in the transition period.
 6. The projectoraccording to claim 4, wherein the third position is an intermediateposition between the first position and the second position.
 7. Theprojector according to claim 6, wherein the image processing circuitsupplies a third image signal based on the input image signal to theelectro-optical panel as the image signal in a third unit period afterthe second unit period among the plurality of unit periods included inone frame period, and supplies a fourth image signal based on the inputimage signal to the electro-optical panel as the image signal in afourth unit period after the third unit period among the plurality ofunit periods, the control circuit controls a state of the optical pathshifting element such that light emitted from the predetermined pixelamong the plurality of pixels reaches a fourth position on the displayscreen in the third unit period, controls a state of the optical pathshifting element such that light emitted from the predetermined pixelreaches a fifth position on the display screen in the fourth unitperiod, and controls a state of the optical path shifting element suchthat light emitted from the predetermined pixel reaches the thirdposition on the display screen in a transition period in which the unitperiod transitions from the third unit period to the fourth unit period,and the third position is an intermediate position between the fourthposition and the fifth position.
 8. The projector according to claim 7,wherein the first position and the second position are positioned in afirst diagonal direction with respect to a direction in which theplurality of pixels are arrayed, and the fourth position and the fifthposition are in a second diagonal direction with respect to thedirection in which the plurality of pixels are arrayed, the seconddiagonal direction being a direction orthogonal to the first diagonaldirection.
 9. The projector according to claim 4, wherein the thirdposition is deviated from an intermediate position between the firstposition and the second position.
 10. The projector according to claim9, wherein the control circuit switches a direction in which a positionof light emitted from a predetermined pixel of the plurality of pixelstransitions from the first position to the third position on the displayscreen and a direction in which a position of the light transitions fromthe third position to the second position based on whether the one frameperiod is a frame period of an odd-numbered frame or a frame period ofan even-numbered frame.
 11. The projector according to claim 10, whereina subframe period including the first unit period, the transitionperiod, and the second unit period is repeated at least twice in the oneframe period, and a position that the light emitted from thepredetermined pixel reaches on the display screen differs in thetransition period in an odd-numbered subframe period of the one frameperiod.
 12. The projector according to claim 1, wherein the controlcircuit causes a transition between the first position and the secondposition based on the type of the image indicated by the input imagesignal.
 13. The projector according to claim 1, wherein the imageprocessing circuit identifies the type of the image using a value ofdifference in luminance between adjacent pixels and outputs typeinformation indicating the identification result to the control circuit.14. A control method for a projector including an electro-optical panelin which a plurality of pixels are arrayed and an optical path shiftingelement configured to change an optical path of light emitted from theplurality of pixels, the control method comprising: supplying a firstimage signal based on an input image signal to the electro-optical panelin a first unit period among a plurality of unit periods included in oneframe period and supplying a second image signal based on the inputimage signal to the electro-optical panel in a second unit period afterthe first unit period among the plurality of unit periods; andcontrolling a state of the optical path shifting element such that lightemitted from a predetermined pixel among the plurality of pixels reachesa first position on a display screen in the first unit period,controlling a state of the optical path shifting element such that lightemitted from the predetermined pixel reaches a second position on thedisplay screen in the second unit period, and controlling, based on atype of image indicated by the input image signal, a state of theoptical path shifting element in a transition period in which a unitperiod transitions from the first unit period to the second unit period.